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Signal transduction inbacterial chemotaxis

Lengeler et al.

pp. 514-523

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Chemotaxis: responses

E. coli !a"es temporal comparisons #esponds to spatial gradients Compares en$ironment o% present &ith

en$ironment o% past 'ime: 1 to 2 sec

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2. sotropic conditions: S ' Sudden increase in *#( , '

(xcitation response / %ast 0 .2 sec

Same *#( ,: S ' Sensor adaptation / slo& sec to min

Conclusion Cell see"s better en$ironment))

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stages

Cell) samples its chemical en$ironment !a"es comparison bet&een current conditions and

past conditions #esponse: i% better suppresses tumbling6 more

smooth s&imming )))))i% &orse no suppression o% tumbling )))))i% no change alternate S ' 7pdates o% short-term memor

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Chemotaxis: components

4 receptor proteins Signal transduction proteins

+daptation proteins

4 receptors

/ meth l-accepting chemotaxis proteins8!C s9

span C!

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4 receptors

'sr'axis serine and some repellents6

Leu / rep6 acids / rep

'ar 'axis aspartate and some repellents !altose / attractant

'rg

'axis ribose and galactose 'ap

'axis to dipeptides

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Chemotaxis: components

Signal transduction proteinsChe+CheChe;Che? 3-----'!1-------- highl $ariable sensor domain ---------'!2-------- lin"er --------!?1-------- se@conser$ation6 signaling domain --------!?2---------CAA?

'! / transmembrane segment

!? / meth lated helix Sensor domain: periplasm Signaling domain: c toplasm

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Signal transduction

(xcitation =ind #( to !C in C! !C sends signal $ia Che;

Che;: adaptor B intermediate in c toplasm Che;: mediates signals to Che+

Che+ / protein "inase

on binding o% #( increased Che+ "inase auto ?is4D increase Che+E

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(xcitation contFd Che+E G Che Che E

Che E +sp5H / tumble %actor Che E binds to Ili! o% %lagellar s&itch Signal / C; rotation / tumbling

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=ind +'' to !C in C! !C sends signal $ia Che; Che; Che+ Che+ / protein "inase

on bdg o% +'' decreased Che+ "inase Lo&er auto lo&er Che+E

Lo&er Che+E G Che lo&er Che E Signal / CC; rotation / smooth

(xcitation / E and deE

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Signal transduction

+daptationChe# G Che= G !C s

*+'', con$erted into intracellular short term

memor registered as meth lated !C

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(xtent o% meth lation a%%ects "inase acti$it o% Che+ #ate o% producing Che E

Complex interpla o% Che# and Che= Autcome:

+daptation restores Che E to same le$elsas be%ore stimulus

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