Chemotaxis in Escherichia coli : Methylation of che gene products

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Abstract
The products of 3 chemotaxis-specific genes in E. coli, cheM, cheD and cheZ, are methylated. The cheZ gene codes for the synthesis of a 24,000 MW polypeptide that appears in the cytoplasm. Gene cheM codes for the synthesis of a membrane-bound polypeptide with a MW of 61,000. Gene cheD codes for another membrane-bound polypeptide with an apparent MW of 64,000. CheM- mutants show chemotaxis toward some attractant (Tar- phenotype), while CheD- mutants respond to other attractants (Tsr- phenotype). The double mutant (CheD-, CheM-) does not respond to any attractant or repellent tested. Therefore, these polypeptides play a central role in chemotaxis. They collect information from 2 subsets of chemoreceptors and act as the last step in the chemoreceptor pathway and the first step in the general processing of signals for transmission to the flagellar rotor. They may be involved in an initial process that reflects the instantaneous state of the chemoreceptors and in an integrative, adaptive process. Two other genes, cheX and cheW, are required for the methylation of the cheD and cheM gene products.