ABSTRACT
Objective To determine the effects of Che A and CheY proteins of Campylobacter jejuni regulating the bacterial chemotaxis in vitro and colonization in vivo. Methods By using pET42a plasmid and E. coli BL21DE3 as expression vector and expression strain, respectively, prokaryotic expression systems of cheA and cheY genes of C. jejuni strain NCTC11168 was constructed. Rabbits were immunized with the target recombinant expression proteins, rCheA and rCheY, to prepare the antisera. rCheA-IgG and rCheY-IgG in the antisera were separated using DEAE-52 ion exchange column. pBluescript- II -SK was applied to construct suicide plasmid which used to generate cheA gene knock-out mutant (cheA-). A chemotaxis model in vitro of C. jejuni based on DOC-HAP, the chemotactic ability of cheA' mutant as well as the effect of rCheA-IgG and closantel inhibiting the bacterial chemotaxis were demonstrated. The phosphorylation levels of CheA and CheY after DOC treatment were examined by using either rCheA-IgG or CheY-IgG capture method. The difference of colonization ability between cheA- mutant and wild-type of C. jejuni in mice were checked and then compared. Results The constructed prokaryotic expression systems could efficiently express rCheA and rCheY. The data from PCR and sequencing confirmed the cheA gene knock out from cheA- mutant chromosome. cheA- mutant lost its chemotactic ability towards DOC. Both the rCheA-IgG and closantel could inhibit the chemotaxis of wild-type of C. jejuni (P < 0.05 ). When treatment of DOC, the phosphorylation levels of CheA and CheY in wild-type of C. jejuni rapidly decreased (P < 0. 05 ). The colonization ability in murine jejunum of cheA- mutant was also lower than that of the wild-type ( P<0.05 ) . Conclusion Chemotaxis-associated two-component signaling system (Che-TCSS) of C. jejuni are composed of CheA and CheY, and the two proteins are activated by dephosphorylation. CheA in the Che-TCSS play a critical role in chemotaxis in vitro and colonization in vivo of C. jejuni, and this protein can be used as a target for developing novel anti- C. jejuni drugs.