A CheZ orthologue in Campylobacter jejuni plays a role in chemotaxis through conserved phosphatase activity

The major food-borne pathogen Campylobacter jejuni employs chemotactic motility to colonise the avian gut, and also as a virulence mechanism in human diarrhoeal disease. In Escherichia coli CheY activity is modulated by CheZ, a phosphatase originally thought to be absent in C. jejuni. The Hp0170 protein of Helicobacter pylori is a distant homologue of CheZ and, as C. jejuni Cj0700 is homologous to HP0170, Cj0700 could also act as a CheZ orthologue in Campylobacter. Both the C. jejuni CheV and CheA proteins also contain a response regulator (RR) domain that may be phosphorylated. Cj0700 would therefore be predicted to dephosphorylate C. jejuni CheY and possibly also the CheV and CheA RR domains. A mutant ({Delta}cj0700) and complement ({Delta}cj0700, cj0046::cj0700) were constructed in C.jejuni strains NCTC11168, NCTC11828 and 81-176. On semisolid agar the {Delta}cj0700 mutant strain showed reduced motility relative to wild-type and this phenotype was reversed in the complemented strain. In pull down and bacterial two hybrid assays, expressed Cj0700 was able to interact with CheY, CheA-RR and CheV. Cj0700 is able to dephosphorylate the RR domain of CheY and CheA-RR, but less efficiently, CheV. These findings verify that Cj0700 plays a role in C. jejuni chemotaxis through phosphatase activity with respect to CheY, and is hence likely to be a CheZ orthologue. Cj0700 also partially modulates the phosphorylation level of the RR domain on CheA and CheV, although the functional consequences of this interaction require further investigation.