Locations of Mapped Genes:
|Superclasses:||Signal transduction pathways|
E. coli movement is typically described as a random three-dimensional walk in which runs of movement in a straight line are punctuated by tumbles as the cell briefly stops and randomly reorients before moving off again. This swimming/tumbling behaviour results from alternating clockwise (tumbling behavior) and counterclockwise (straight swimming behavior) flagellar rotation. Chemotaxis is the ability of E. coli to move or 'swim' towards or away from specific chemical attractants and repellents and is achieved by regulating the probability of CW and CCW flagella rotation via a modified two-component signal transduction pathway - the chemotactic signal transduction pathway. Pathway components include the dual function histidine kinase CheA, the response regulators CheY and CheB, plus CheW, CheR, and the transmembrane receptor proteins.
CheA is a dual function cytoplasmic histidine kinase which, in conjunction with one of the transmembrane receptor proteins (the so-called methyl accepting chemotaxis proteins - Tsr, Tar, Trg or Tap) and a linker protein CheW, forms a ternery signalling complex (MCPI, MCPII, MCPIII or MCPIV). Ligands interact with the receptor proteins and affect the flow of phosphoryl groups from CheA to two response regulators - CheY and CheB - neither of these proteins are transcription factors unlike the majority of two-component response regulators in E. coli. CheY influences flagella rotation by direct binding to the FliM protein - a component of the flagella motor switch complex. CheY and phosphoCheY bind to FliM with different affinities and influence the direction of flagellar rotation. CheB is a methylesterase which, along with CheR methyltransferase takes part in a feedback loop that enables the pathway to adapt to background stimuli.
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