microfilament actin 1

8/17/2019 Microfilament Actin 1

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MICROFILAMENT ACTIN



Microfilament

(thin filament)structure

QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this

25nm

--- 7-8nm

G-actin

monomer

ATP

minus

plus



MIKROFILAMEN

diameter 60 angstrom

consist of actin protein

molecule.



4

Actin Filaments

Thinner, shorter and more flexible thanmicrotubules

Contains G-actin, and -actin Actin- most abundant intracellular

protein in most !u"ar#otic cells

Comprises $%& b# 'ei(ht of total cellprotein in muscle cells, $-5& in non-muscle cells



G-actin and F-actin

G-actin) exists as a (lobular monomer

-actin) is a helical filamentous pol#mer of G-

actin subunits all oriented in the samedirection

*icrofilaments in a cell are constantl#

shrin"in( or (ro'in( in len(th

+undles and mesh'or"s of microfilaments

are formin( and dissolin( continuousl#



A"tin merupa"an protein

(lobular, dalam bentu"monomer disebut a"tin G, #an(

dapat dira"it menadi filamen

ran("ap #an( disebut a"tin

A"tin mudah terurai menadimonomer-monomern#a dan

tera"it "embali menadi

mi"rofilamen

A"tin terlibat dalam proses-proses #an( teradi dalam sel

.sito"inesis, aliran plasma,

(era"an sel, (era"an mi"roili

intestinal, dsb/

Aktin GAktin F



!namics of Actin Assem"l!

0ucleation- G-actin clumps into short,unstable oli(omers, 1-4 subunits lon(, and

acts as a stable nucleus, proteins include

the Arp21 complex .actin nucleator/ or bindin( nucleator) tandem-monomer-

bindin( nucleators3

!lon(ation phase- increases in len(thb# the addition of actin monomers to ./

end b# protein formin



!namics of Actin Assem"l!

6tead#-6tate

The ends of actin filaments are in a stead#

state 'ith monomeric G-actin After their incorporation into a filament,

subunits slo'l# h#drol#e ATP and become

stable -actin

Protein profilin, 'hich catal#es AP to ATP

exchan(e and Acofilin, 'hich mediates

filament disassembl#



Copyright (c) by W. H. Freeman and Company

Nucleation, Elongation, and the Steady-State

Figure 18-11



FILAMEN AKTIN

iumpai seba(ai arin(-

arin( trimatra #an( "a"u,

"arena filamen a"tin

san(at teri"at den(an

protein pen(i"at silan(

.cros lin"in(/ Protein pen(i"at silan(

#an( ban#a" terdapat di

dalam sel #aitu filamin,#aitu suatu mole"ul

panan( dan lentur terdiri

dari dua rantai polipeptida

"embar



All subunits in an actin filament point to'ardthe same direction of the filament !xhibits polarit#-actin subunit exposed to the

surroundin( solution is the .-/ end

The cleft that has contact 'ith the nei(hborin(actin subunit that is not exposed is the ./ end

Actin filaments (ro' faster at the ./ end than the.-/ end



F-actin has structural and functional

polarity



$9

Actin Filaments #artici#ate in a

$ariet! of cell functions% Anchora(e and moement of

membrane proteins- filaments are distributed in 1-dimensional

net'or"s throu(hout the cell

used as anchors 'ith in specialied cell

unctions




$ariet! of cell functions% ormation of the structural core of

microilli

:n epithelial cells, help maintain shape ofthe cell surface



MIKROILIo

Adala! ton"olan#ton"olan$er$entu% "ari &ang terdapat dipermu%aan sel' terutama sel!e(an

o )an"angn&a se%itar satumi%rometer' dan garis

tenga!n&a *0 nanometero +agian tenga! mi%ri,ili $erisi

se$er%as -lamen#-lamen a%tin&ang tersusun se"a"ar satuter!adap &ang lain' denganu"ung positifn&a mengara! %epermu%aan sel

o Filamen#-lamen terse$utdi!u$ung%an satu dengan &anglain ole! protein#proteinpengi%at &aitu -m$rin' ,ilin'

dan %omple%s calmodulin.




$ariet! of cell functions% ;ocomotion of the cells

Achieed b# the force exerted b# actin

filaments b# pol#meriation at their (ro'in(ends

<sed in man# mi(ratin( cells, particularl#on transformed cells of inasie tumors

Cells extend processes from their surfaceb# pushin( the plasma membrane aheadof the (ro'in( actin filaments

microfilament actin 1

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