十字花科黑腐病菌中類纖毛蛋白XpsG、H、I、J 和 K間交互作用關係的探討

Abstract

Xanthomonas campestris pv. Campestris is one of the Gram-negtive bacteria which secretes protein to infect plants by typeⅡ secretion system. The secreted protein can reach to periplasm by the Sec-dependent system, and to export from cellular matrix by a machine composed of 12~14 proteins. The N terminal of XpsG, H, I , J and K protein are homologous with the pilin of typeⅣ secretion system, those are predicted to be assembled into a pilus-like structure between the cytoplasmic and outer membrane. The pseudopilus is presumed to push exproteins into the outer membrane. On previous studys showed that XpsG was a mainly composed of pseudopilus to span between inner and outer membrane, and could regulate the interaction between XpsG and XpsJ, and thought that XpsG, I, H and J should act sequentially in such order. We have prepared specific antibody against XpsK that be used to analyze the interaction between XpsG、H、I、J and K in various bacterial strains with different xps gene knockout after Ni2+ affinity chromatography. Result revealed that XpsI could inhibit the interaction between XpsH and XpsJ, and act as a negative regulator. XpsK could promote the interaction between XpsI and XpsJ, act as a positive regulator. Take together, we believed that XpsG and XpsJ are located at a extremity of pseudopilin complex , and there are three interaction forms between XpsH, I and K , including XpsH-XpsI, XpsH-XpsK and XpsI-XpsK. We believe that the copmposed of the pseudopilus is a complicated mechanism, and need more experiments to explain any possibility.