A CheZ orthologue inCampylobacter jejuniplays a role in chemotaxis through conserved phosphatase activity

Abstract

AbstractThe major food-borne pathogenCampylobacter jejuniemploys chemotactic motility to colonise the avian gut, and also as a virulence mechanism in human diarrhoeal disease.InEscherichia coliCheY activity is modulated by CheZ, a phosphatase originally thought to be absent inC. jejuni. The Hp0170 protein ofHelicobacter pyloriis a distant homologue of CheZ and, asC. jejuniCj0700 is homologous to HP0170, Cj0700 could also act as a CheZ orthologue inCampylobacter. Both theC. jejuniCheV and CheA proteins also contain a response regulator (RR) domain that may be phosphorylated. Cj0700 would therefore be predicted to dephosphorylateC. jejuniCheY and possibly also the CheV and CheA RR domains.A mutant (Δcj0700)and complement (Δcj0700, cj0046::cj0700) were constructed inC.jejunistrains NCTC11168, NCTC11828 and 81-176. On semisolid agar the Δcj0700mutant 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 inC. jejunichemotaxis 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.