CELLSBenjamin Lewi n

Lynne Cassimeri s

Vishwanath R . Lingappa

George Plopper

PrefaceAcknowledgments iv

Olntermediate filaments 411E . Birgitte Lan e

About the cover vContributors xvii

Part 5 Cell division, apoptosis ,

Abbreviations xix

and cancer

43 8

OMitosis 43 9Part 1 Introduction

1

Conly Riede r

©What is a cell? 3

OCell cycle regulation 489Benjamin Lewin

Srinivas Venkatram, Kathleen L . Gould, and Susan L . Forsbur g

OApoptosis 53 3Membranes and transport

Douglas R . Gree n

mechanisms

30

®Cancer-Principles and overview 56 1Robert A . Weinber g

©Transport of ions and small molecules acros smembranes 31

Part 6 Cell communication

587Stephan E . Lehnart and Andrew R. Mark s

© Membrane targeting of proteins 97

®Principles of cell signaling 58 9Melanie H . Cobb and Elliott M . Ros sD . Thomas Rutkowski and Vishwanath R . Lingappa

©Protein trafficking between membranes 153

OThe extracellular matrix and cell adhesion 64 5Graham Warren and Ira Mellman

George Plopper

Part 3 The nucleus

204

Part 7 Prokaryotic and plant cells 70 3

0Nuclear structure and transport 205

'Prokaryotic cell biology 70 5Charles N . Cole and Pamela A . Silver

Jeff Errington, Matthew Chapman, Scott J . Hultgren, andMichael Caparon

()Chromatin and chromosomes 253

OPlant cell biology 76 3Benjamin Lewin

Give Lloy d

Part 4 The cytoskeleton

316

Glossary 80 7

0Microtubules 317

Protein database index 82 5Lynne Cassimeris

Index 827OActi n 37 1Enrique M. De La Cruz and E . Michael Ostap

Preface

Protein folding and unfolding is an essential feature o fall cells

23Acknowledgments iv

1 .18

The shape of a eukaryotic cell is determined by it sAbout the cover v

cytoskeleton 2 4

Contributors xviil i Localization of cell structures is important 2 51 .2o

Signal transduction pathways execute predefine dAbbreviations xix

responses 26

® All organisms have cells that can grow and divide 2 7

Part 1 Introduction

1

i Differentiation creates specialized cell types, includin gterminally differentiated cells 2 8

1 What is a cett?

3

References 2 9

Benjamin Lewin

1 Introduction 4

Membranes an dLife began as a self-replicating structure 6

transport mechanisms

3 0® A prokaryotic cell consists of a single compartment 7

Kin Prokaryotes are adapted for growth under many diverse

2 Transport of ions and smallconditions 9

Ign A eukaryotic cell contains many membrane-delimited

motecutes across membranes . . . 3 1compartments 9

Stephan E. Lehnart and Andrew R. Marks1 .6

Membranes allow the cytoplasm to maintain Introduction 32compartments with distinct environments 10 glM Channels and carriers are the main types of membran eThe nucleus contains the genetic material and is

transport proteins 3 3surrounded by an envelope 12

Hydration of ions influences their flux throug h® The plasma membrane allows a cell to maintain

transmembrane pores 3 5homeostasis 13

Electrochemical gradients across the cell membran eCells within cells : Organelles bounded by envelopes may

generate the membrane potential 3 6have resulted from endosymbiosis 15 ain K+ channels catalyze selective and rapid ionDNA is the cellular hereditary material, but there are

permeation 38other forms of hereditary information 17

2 .6

Different K+ channels use a similar gate coupled t o® Cells require mechanisms to repair damage to DNA 17

different activating or inactivating mechanisms 4 2WEI Mitochondria are energy factories 18

® Voltage-dependent Na+ channels are activated by® Chloroplasts power plant cells 19

membrane depolarization and translate electrica lOrganelles require mechanisms for specific localization of

signals 44

proteins 20

raga Epithelial Na+ channels regulate Na+ homeostasis 4 7IMO Proteins are transported to and through membranes 21

2 .9

Plasma membrane Cat+ channels activate intracellula r® Protein trafficking moves proteins through the ER and

functions 50Golgi apparatus 22

® Cl- channels serve diverse biological functions 52

® Selective water transport occurs through aquaporin

3 .8

Some proteins target and translocat echannels

56

posttranslationally

110

Action potentials are electrical signals that depend on

3 .9

ATP hydrolysis drives transtocation

11 1several types of ion channels 58

3 .10

Transmembrane proteins move out of the translocatio nCardiac and skeletal muscles are activated by excitation-

channel and into the Lipid bilayer 11 3contraction coupling 60

® The orientation of transmembrane proteins is determine d® Some glucose transporters are uniporters 63

as they are integrated into the membrane 11 5Symporters and antiporters mediate coupled

® Signal sequences are removed by signal peptidase 11 8transport 65 ® The Lipid GPI is added to some translocate d

2 .16

The transmembrane Na+ gradient is essential for the

proteins

118function of many transporters 67

® Sugars are added to many translocating proteins 12 0® Some Na+ transporters regulate cytosolic or extracelLular

Chaperones assist folding of newly translocate dpH 70

proteins 12 12 .18

The Ca t+-ATPase pumps Ca t + into intracellular storage

3 .16

Protein disulfide isomerase ensures the formation of th ecompartments 73

correct disulfide bonds as proteins fold 12 22 .19

The Na+/K+-ATPase maintains the plasma membrane Na+

® The calnexin/calreticulin chaperoning system recognizesand K+ gradients 75

carbohydrate modifications 12 32 .20

The F1 Fo -ATP synthase couples H+ movement to ATP

3 .18

The assembly of proteins into complexes i ssynthesis or hydrolysis 78

monitored 124® H+-ATPases transport protons out of the cytosol 79

3 .19

Terminally misfolded proteins in the ER are returned t o® What's next? 82

the cytosol for degradation 125® Summary 82

3 .20 Communication between the ER and nucleus prevents th e® Supplement : Derivation and application of the Nernst

accumulation of unfolded proteins in the Lumen 12 8

equation 83

® The ER synthesizes the major cellula r

Supplement : Most K+ channels undergo rectification 85

phospholipids 13 0

2 .26

Supplement : Mutations in an anion channel cause cystic

Lipids must be moved from the ER to the membranes o ffibrosis 86

other organelles 13 2

References 88

The two leaflets of a membrane often differ in lipi dcomposition 133

Membrane targeting of

® The ER is morphologically and functionall ysubdivided 13 3

proteins 97

The ER is a dynamic organelle 13 5

D. Thomas Rutkowski and Vishwanath R . Lingappa

3 .26

Signal sequences are also used to target proteins t o

Introduction 98

other organelles 138

Proteins enter the secretory pathway by translocation

® Import into mitochondria begins with signal sequenc e

across the ER membrane (an overview) 100

recognition at the outer membrane 13 8

Proteins use signal sequences to target to the ER for3 .28

Complexes in the inner and outer membranes cooperate

translocation

102

in mitochondria) protein import 13 9

® Signal sequences are recognized by the signal

Proteins imported into chloroplasts must also cross tw o

recognition particle (SRP) 103

membranes 14 1

® An interaction between SRP and its receptor allows

Proteins fold before they are imported into

proteins to dock at the ER membrane 104

peroxisomes 142

The translocon is an aqueous channel that conducts

What's next? 144

proteins 105

3 .32

Summary 144

Translation is coupled to translocation for most

References 146

eukaryotic secretory and transmembrane proteins 108

Protein trafficking between

Part 3 The nucleus

204membranes 15 3Graham Warren and Ira Mellman

5 Nuclear structure and transport 20 5® Introduction 154

Charles N . Cole and Pamela A . Silver

Overview of the exocytic

® Introduction 206pathway 156

® Nuclei vary in appearance according to cell type an d® Overview of the endocytic pathway 159

organism 20 7

® Concepts in vesicle-mediated protein

Chromosomes occupy distinct territories 20 9transport 162

® The nucleus contains subcompartments that are no tThe concepts of signal-mediated and bulk flow protein

membrane-bounded 21 0transport 164

® Some processes occur at distinct nuclear sites and may

4 .6

COPII-coated vesicles mediate transport from the ER to

reflect an underlying structure 21 2the Golgi apparatus 166

5 .6

The nucleus is bounded by the nuclear envelope 21 3® Resident proteins that escape from the ER are

The nuclear lamina underlies the nuclear envelope 214retrieved 168

5 .8

Large molecules are actively transported between th e

4 .8

COPI-coated vesicles mediate retrograde transport from

nucleus and cytoplasm 21 6the Golgi apparatus to the ER 169

5 .9

Nuclear pore complexes are symmetrical channels 21 7

4 .9

There are two popular models for forward transport

5 .10

Nuclear pore complexes are constructed fro mthrough the Golgi apparatus 171

nucleoporins 2204 .10

Retention of proteins in the Golgi apparatus depends o nthe membrane-spanning domain 172

Proteins are selectively transported into the nucleu sthrough nuclear pores 22 2

Rab GTPases and tethers are two types of proteins tha tregulate vesicle targeting 174

® Nuclear localization sequences target proteins to th enucleus 224

▪ SNARE proteins likely mediate fusion of vesicles wit htarget membranes 176

Cytoplasmic NLS receptors mediate nuclear protei nimport 224

® Endocytosis is often mediated by clathrin-coate dvesicles 179

® Export of proteins from the nucleus is also receptor -mediated 226

® Adaptor complexes link clathrin and transmembran ecargo proteins 182

® The Ran GTPase controls the direction of nuclea rtransport 228

® Some receptors recycle from early endosomes whereas

5 .16 Multiple models have been proposed for the mechanis mothers are degraded in lysosomes

185

of nuclear transport

230Early endosomes become late endosomes and lysosomesby maturation 187

® Nuclear transport can be regulated 23 2

Sorting of tysosomal proteins occurs in the trans-Golgi

5 .18

Multiple classes of RNA are exported from the®

network 189

nucleus 233

5 .19

Ribosomal subunits are assembled in the nucleolus an d® Polarized epithelial cells transport proteins to apical and

exported by exportin 1 235basolateral membranes 19 2

19

Some cells store proteins for Later

5 .20

tRNAs are exported by a dedicated exportin 23 6

secretion 194

Messenger RNAs are exported from the nucleus as RNA

® What's next? 195

protein complexes 23 7

® Summary 196

® hnRNPs move from sites of processing to NPCs 23 9

References 196

mRNA export requires several novel factors 23 9

U snRNAs are exported, modified, assembled intocomplexes, and imported 24 1

® Precursors to microRNAs are exported from the nucleu sand processed in the cytoplasm 242

5 .26

What's next? 242

6 .28

Chromatin remodeling is an active process 29 2Summary 245

6 .29

Histone acetylation is associated with geneti cReferences 246

activity 2966 .30

Heterochromatin propagates from a nucleatio nevent 2996 Chromatin and chromosomes . . 253

6 .31 Heterochromatin depends on interactions withBenjamin Lewin

histones 30 06 .1

Introduction 254

6 .32

X chromosomes undergo global changes 30 26 .2

Chromatin is divided into euchromatin and

6 .33

Chromosome condensation is caused byheterochromatin 255

condensins 30 46 .3

Chromosomes have banding patterns 256

6 .34

What's next? 30 66 .4

Eukaryotic DNA has loops and domains attached to a

6 .35

Summary 30 7scaffold 258

References 30 96 .5

Specific sequences attach DNA to an interphasematrix 259

6 .6 The centromere is essential for

Part 4 The cytoskeleton

31 6segregation 260

6 .7

Centromeres have short DNA sequences in

7 Microtubules 31 7S. cerevisiae 262

Lynne Cassimeris6 .8

The centromere binds a protein complex

263® Introduction 31 8

6 .9

Centromeres may contain repetitious DNA 263® General functions of microtubutes 32 0

6 .10

Telomeres are replicated by a specia lmechanism 264

® Microtubules are polar polymers of a- an dj3-tubulin

32 3® Telomeres seal the chromosome ends 265

Purifie dLampbrush chromosomes are extended 266

®

tubulin subunits assemble intomicrotubules 32 5

® Polytene chromosomes form bands 267

® Microtubule assembly and disassembly proceed by a6 .14

Polytene chromosomes expand at sites of

unique process termed dynamic instability 327gene expression 268

® A cap of GTP-tubulin subunits regulates the transitions of6 .15

The nucteosome is the subunit of all

dynamic instability 32 9chromatin 269

® Cells use microtubute-organizing centers to nucleat e® DNA is coiled in arrays of nucleosomes 271

microtubule assembly 33 16 .17

Nucleosomes have a common structure 272

7 .8

Microtubule dynamics in cells 33 36 .18

DNA structure varies on the nucleosomal surface 274

Why do cells have dynamic microtubutes? 33 66 .19

Organization of the histone octamer 276

Cells use several classes of proteins to regulate th e® The path of nucleosomes in the chromatin fiber 278

stability of their microtubules 33 9

® Reproduction of chromatin requires assembly of

® Introduction to microtubule-based motor proteins 34 2nucleosomes 279

® How motor proteins work 346® Do nucleosomes lie at specific positions? 282

® How cargoes are loaded onto the right motor 34 9® Domains define regions that contain active genes 285

® Microtubule dynamics and motors combine to generateAre transcribed genes organized in nucleosomes? 287

the asymmetric organization of cells 350

® Histone octamers are displaced by transcription 288

® Interactions between microtubutes an d

® Nucleosome displacement and reassembly require special

actin filaments 354

factors 290

® Cilia and flagella are motile structures 35 6

® DNAase hypersensitive sites change chromatin

® What's next? 36 1

structure 290

Summary 362

® Supplement: What if tubulin didn't hydrolyze GTP? 363

8 .23 Summary 40 4

7 .20

Supplement: Fluorescence recovery after

8 .24

Supplement: Two models for how polymer assembly ca nphotobleaching

364

generate force 40 4

® Supplement : Tubulin synthesis and modification 365

References 405

® Supplement: Motility assays for microtubule-based moto rproteins 366

9 Intermediate filaments 41 1References 368

E. Birgitte Lane

9 . 1Actin 371

.1

Introduction

41 2

9 .2

The six intermediate filament protein groups have simila rEnrique M. De La Cruz and E. Michael Ostap

structure but different expression 41 3

8--

Introduction 372

9 .3

The two largest intermediate filament groups are type IActin is a ubiquitously expressed cytoskeletal

and type II keratins 415

protein

373

9 .4

Mutations in keratins cause epithelial cell fragility 41 8

® Actin monomers bind ATP and ADP 373

9 .5

Intermediate filaments of nerve, muscle, and connectiv e® Actin filaments are structurally polarized polymers 374

tissue often show overlapping expression 420

8 .5

Actin polymerization is a multistep and

® Lamin intermediate filaments reinforce the nuclea rdynamic process 375

envelope 42 2

8 .6

Actin subunits hydrolyze ATP after polymerization 378

9 .7

Even the divergent lens filament proteins are conserve d

Actin-binding proteins regulate actin polymerization and

in evolution 424

organization 380

9 .8

Intermediate filament subunits assemble with hig haffinity into strain-resistant structures

42 5® Actin monomer-binding proteins influenc epolymerization 381

q , a

Posttranslational modifications regulate th e

Nucleating proteins control cellular actinconfiguration of intermediate filament proteins 427

polymerization 382

9 .10

Proteins that associate with intermediate filaments ar e

® Capping proteins regulate the length of actin

facultative rather than essential 42 9

filaments 383

® Intermediate filament genes are present throughou t

® Severing and depolymerizing proteins regulate actin

metazoan evolution 430

filament dynamics 384

® What's next? 43 2

® Crosslinking proteins organize actin filaments into

® Summary 433

bundles and orthogonal networks 385

References 43 4

Actin and actin-binding proteins work together to driv ecell migration 386

Part 5 Cell division ,® Small G proteins regulate actin polymerization 388

▪ Myosins are actin-based molecular motors with essential apoptosis, and cancer 438roles in many cellular processes 389

® Myosins have three structural domains 392

10 Mitosis 43 9▪ ATP hydrolysis by myosin is a multistep Canty Rieder

reaction 39 4

Myosin motors have kinetic properties suited for their

Introduction 440

cellular roles 396

® Mitosis is divided into stages 44 3

WEI Myosins take nanometer steps and generate piconewton

gni Mitosis requires the formation of a new apparatus calle dforces 396

the spindle 445

• Myosins are regulated by multiple mechanisms 398 Spindle formation and function depend on the dynami c

Myosin-II functions in muscle contraction 399

behavior of microtubules and their associated moto rproteins 447IMEB What ' s next? 403Centrosomes are microtubule organizing centers 450

10 .6

Centrosomes reproduce about the time the DNA is

® The cell cycle as a cycle of CDK activities 49 6replicated 451 CDK-cyclin complexes are regulated in severa l

10 .7

Spindles begin to form as separating asters

ways 498interact 453

11 .6

Cells may exit from and reenter the cell cycle 50 110 .8

Spindles require chromosomes for stabilization but can

® Entry into cell cycle and S phase is tightly"self-organize" without centrosomes 456

regulated 50310 .9

The centromere is a specialized region on the chromo-

11 .8

DNA replication requires the ordered assembly of protei nsome that contains the kinetochores 458

complexes 50410 .10

Kinetochores form at the onset of prometaphase and

U.S

Mitosis is orchestrated by several protein kinases 50 7contain microtubule motor proteins 459

11 .10 Many morphological changes occu r10 .11

Kinetochores capture and stabilize their associated

during mitosis 51 0microtubules 460

® Mitotic chromosome condensation and segregatio nMIS Mistakes in kinetochore attachment are corrected 463

depend on condensin and cohesin 51 2® Kinetochore fibers must both shorten and elongate to

® Exit from mitosis requires more than cycli nallow chromosomes to move 465

proteolysis 51 410 .14 The force to move a chromosome toward a pole is

® Checkpoint controls coordinate different cellproduced by two mechanisms 467

cycle events 51610.15 Congression involves pulling forces that act on the

® DNA replication and DNA damage checkpoints monito rkinetochores 468

defects in DNA metabolism 51 810 . .6 Congression is also regulated by the forces that act along

® The spindle assembly checkpoint monitors defects i nthe chromosome arms and the activity of sister

chromosome-microtubule attachment 52 2kinetochores 469

11 .16

Cell cycle deregulation can lead to cancer 52 4® Kinetochores control the metaphase/anaphas e

transition 471

® What's next? 52 5

® Anaphase has two phases 473

11 .18 Summary 52 6

® Changes occur during telophase that lead the cell out of

References 52 7

the mitotic state 47 5

® During cytokinesis, the cytoplasm is partitioned to form

12 Apoptosis 53 3two new daughter cells 476

Douglas R. Green® Formation of the contractile ring requires the spindle an d

stem bodies 478

Introduction 534

The contractile ring cleaves the cell in two 481

® Caspases orchestrate apoptosis by cleaving specifi csubstrates 536

® The segregation of nonnuclear organelles durin gcytokinesis is based on chance 483

Executioner caspases are activated by cleavage, wherea sinitiator caspases are activated by dimerization

537® What' s next? 483

Some inhibitor of apoptosis proteins (IAPs) block® Summary 484

caspases 53 8References 485

® Some caspases have functions in inflammation 53 9The death receptor pathway of apoptosis transmits

11 Cell cycle regulation 489

external signals 53 9

Srinivas Venkatram, Kathleen L . Gould, and

® Apoptosis signaling by TNFR1 is complex 54 1

Susan L . Forsburg

® The mitochondria) pathway of apoptosis 543

® Introduction 490

Bcl-2 family proteins mediate and regulate MOMP an d

® There are several experimental systems used in cell cycleapoptosis 544

analyses 491

® The multidomain Bd.-2 proteins Bax and Bak are required

® The cell cycle requires coordination betweenfor MOMP 54 5

events 495

® The activation of Bax and Bak are controlled by othe rBcl-2 family proteins 546

EYE Cytochrome c, released upon MOMP, induces caspase

® Access to vital supplies is provided byactivation 547

angiogenesis 58 2

® Some proteins released upon MOMP block IAPs 548

® Cancer cells may invade new locations in the body 583

12 .14 The death receptor pathway of apoptosis can engage

What's next? 584MOMP through the cleavage of the BH3-only

13 .16 Summary 58 5protein Bid 548

References 58512 .15 MOMP can cause "caspase-independent" cell death 550

12 .16 The mitochondrial permeability transition can cause

Dart 6 CellMOMP 550

f

® Many discoveries about apoptosis were made in communication 587nematodes 551

® Apoptosis in insects has features distinct from mammal sand nematodes 552

14 Principles of cell signaling . . . . 58 912 .19 The clearance of apoptotic cells requires cellular

Melanie H. Cobb and Elliott M . Rossinteraction

553 Introduction 59 0® Apoptosis plays a role in diseases such as viral infection

Cellular signaling is primarily chemical 59 1and cancer 55 4

® Apoptotic cells are gone but not forgotten 555

® Receptors sense diverse stimuli but initiate a limite drepertoire of cellular signals

592•

What's next? 556 ® Receptors are catalysts and amplifiers 59 3® Summary 557 Ligand binding changes receptor conformation 59 3

References 557 Signals are sorted and integrated in signaling pathway sand networks 59 5

13 Cancer-Principles and

® Cellular signaling pathways can be thought of a s

overview 561

biochemical logic circuits 597

14 .8

Scaffolds increase signaling efficiency and enhanceRobert A . Weinberg

spatial organization of signaling 59 8® Tumors are masses of cells derived from a

® Independent, modular domains specify protein-protei nsingle cell 562

interactions 600▪ Cancer cells have a number of phenotypic Cellular signaling is remarkably adaptive 60 2

characteristics

563 ® Signaling proteins are frequently expressed as multipl e▪ Cancer cells arise after DNA damage 566 species 604® Cancer cells are created when certain genes

® Activating and deactivating reactions are separate an dare mutated 567

independently controlled 60 5

® Cellular genomes harbor a number of

Cellular signaling uses both allostery and covalen tproto-oncogenes 569

modification 606

® Elimination of tumor suppressor activity requires two ® Second messengers provide readily diffusible pathwaysmutations 570

for information transfer 606The genesis of tumors is a complex process 572

IBM Ca2 + signaling serves diverse purposes in all eukaryoti c

▪ Celt growth and proliferation are activated by cells 60 8growth factors 575

Lipids and lipid-derived compounds are signalin g

was Cells are subject to growth inhibition and may exit from

molecules 609the cell cycle 577

® PI 3-kinase regulates both cell shape and the activatio n

Tumor suppressors block inappropriate entry into the cell

of essential growth and metabolic functions 61 2cycle 579

gEl Signaling through ion channel receptors isMutation of DNA repair and maintenance genes can

very fast 612increase the overall mutation rate 580

gan) Nuclear receptors regulate transcription 61 4Cancer cells may achieve immortality 581

14 .20 G protein signaling modules are widely used and highly

® Vitronectin facilitates targeted cell adhesion durin gadaptable 615

blood clotting 65 8

® Heterotrimeric G proteins regulate a wide variety of

15 .8

Proteoglycans provide hydration to tissues 65 9effectors 618

15 .9

Hyaluronan is a glycosaminoglycan enriched i nHeterotrimeric G proteins are controlled by a regulatory

connective tissues 662GTPase cycle 618

15 .10

Heparan sulfate proteoglycans are cell surfac eSmall, monomeric GTP-binding proteins are multiuse

coreceptors 66 4switches 620 ® The basal Lamina is a specialized extracellula rProtein phosphorylation/dephosphorylation is a major

matrix 66 6regulatory mechanism in the cell 621

® Proteases degrade extracellular matri xTwo-component protein phosphorylation systems are

components 66 7signaling relays 624

® Most integrins are receptors for extracellular matrix14 .26

Pharmacological inhibitors of protein kinases may be

proteins

670used to understand and treat disease 625

® Integrin receptors participate in cell signaling 67 2® Phosphoprotein phosphatases reverse the actions of

® Integrins and extracellular matrix molecules play keykinases and are independently regulated

625

roles in development 67614 .28 Covalent modification by ubiquitin and ubiquitin-like

15 .16 Tight junctions form selectively permeable barrier sproteins is another way of regulating protein

between cells 67 7function 626

® Septate junctions in invertebrates are similar to tight14 .29 The Wnt pathway regulates cell fate during development

junctions 68 0and other processes in the adult 628

15 .18 Adherens junctions link adjacent cells 68 214 .30

Diverse signaling mechanisms are regulated by protein

15 .19

Desmosomes are intermediate filament based cel ltyrosine kinases 628

adhesion complexes 684® Src family protein kinases cooperate with receptor

15 .20 Hemidesmosomes attach epithelial cells to the basa lprotein tyrosine kinases 630

lamina 686MAPKs are central to many signaling pathways 631

® Gap junctions allow direct transfer of molecules betwee nCyclin-dependent protein kinases control the

adjacent cells 688cell cycle 632 ® Calcium-dependent cadherins mediate adhesion betwee nDiverse receptors recruit protein tyrosine kinases to the

cells 690plasma membrane 633 ® Calcium-independent NCAMs mediate adhesion betwee n

® What's next? 637

neural cells 69 214 .36 Summary 637

Selectins control adhesion of circulatin gReferences 637

immune cells 694

What's next? 696

15 The extracellular matrix and cell

15 .26 Summary 696

adhesion 645

References 69 7

George Plopper

® Introduction 646

Part 7 Prokaryotic an d® A brief history of research on the extracellular

plant cells

703matrix 648Collagen provides structural support to tissues 649

16 Prokaryotic cell biology 705'13 Fibronectins connect cells to collagenous matrices 652

JeffErrington, Matthew Chapman, Scott J . Hultgren ,Elastic fibers impart flexibility to

and Michael Caparo ntissues

654Laminins provide an adhesive substrate for cells 656

® Introduction 706

® Molecular phylogeny techniques are used to understan dmicrobial evolution 708

16 .3

Prokaryotic lifestyles are diverse 709

® How plants grow 76 5

16 .4

Archaea are prokaryotes with similarities to eukaryotic

® The meristem provides new growth modules in acells 711

repetitive manner 766

16 .5

Most prokaryotes produce a polysaccharide-rich Layer

an The plane in which a cell divides is important for tissu ecalled the capsule 713

organization 768

16 .6

The bacterial cell wall contains a crosslinked meshwork

® Cytoplasmic structures predict the plane of cell divisio nof peptidoglycan 716

before mitosis begins 770

16 .7

The cell envelope of Gram-positive bacteria has unique

17 .6

Plant mitosis occurs without centrosomes 772features 720

® The cytokinetic apparatus builds a new wall in the plan e16 .8

Gram-negative bacteria have an outer membrane and a

anticipated by the preprophase band 774periplasmic space 722

17 .8

Secretion during cytokinesis forms the cell plate 77616 .9

The cytoplasmic membrane is a selective barrier for

17 .9

Plasmodesmata are intercellular channels that connectsecretion 725

plant cells 77 716 .10 Prokaryotes have several secretion pathways 726

17 .10 Cell expansion is driven by swelling of the vacuole 77916 .11 Pili and flagella are appendages on the cell surface of

® The large forces of turgor pressure are resisted by th emost prokaryotes 728

strength of cellulose microfibrils in the cell wall 78016 .12 Prokaryotic genomes contain chromosomes and mobile

® The cell wall must be loosened and reorganized to allo wDNA elements 731

growth 78216 .13 The bacterial nucleoid and cytoplasm are

® Cellulose is synthesized at the plasma membrane, no thighly ordered 733

preassembled and secreted like other wal l16 .14 Bacterial chromosomes are replicated in specialized

components 784replication factories 735

® Cortical microtubules are thought to organize16 .15 Prokaryotic chromosome segregation occurs in the

components in the cell wall 78 5absence of a mitotic spindle 737

® Cortical microtubules are highly dynamic and can chang e16 .16 Prokaryotic cell division involves formation of a complex

their orientation 787cytokinetic ring 739

17 .16

A dispersed Golgi system delivers vesicles to the cel l16 .17 Prokaryotes respond to stress with complex

surface for growth 790developmental changes 742

® Actin filaments form a network for delivering material s16 .18 Some prokaryotic life cycles include obligatory

around the cell 79 1

developmental changes 746

17 .18 Differentiation of xylem cells requires extensiv e16 .19 Some prokaryotes and eukaryotes have endosymbiotic

specialization 793

relationships 747

17 .19 Tip growth allows plant cells to extend processes 79516 .20 Prokaryotes can colonize and cause disease in higher

17 .20 Plants contain unique organelles called plastids 797organisms 749 ® Chloroplasts manufacture food fro m

® Biofilms are highly organized communities of

atmospheric CO 2 799microbes 751 ® What's next? 801

16 .22 What's next? 754 ® Summary 80 1® Summary 754

References 803References 755

Glossary 807

17 Plant cell biology 763

Protein database index 82 5Clive Lloyd

Index 82 7® Introduction

764