Cyclic di-GMP regulate XcOPPs activity by binding with a novel receptor protein XcYajQ

• Main Authors: Chi-Ning Wan, 萬騏寧
• Other Authors: Shan-Ho Chou
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/10656219850574920055

碩士 === 國立中興大學 === 生物化學研究所 === 103 === Cyclic di-guanylate (cyclic di-GMP) is an unique and important second messenger in bacteria which regulates many critical processes include motility, biofilm formation and virulence. But it may play additional functions that are to be uncovered . Recent study found that XcYajQ, a YajQ family protein from the plant pathogen Xanthomonas campestris pv. Campestris (Xcc), is a novel receptor of cyclic di-GMP. Importantly, XcYajQ is able to interact with a variety of other proteins to alter their function. Octaprenyl pyrophosphate synthase (OPPs) is one of these identified proteins which can interact with XcYajQ with strong affinity. XcOPPs catalyzes the formation of a C40 long-chain product OPP that serves as the side chain of ubiquinone and menaquinone by using one allylic substrate farnesyl pyrophosphate (FPP) and five homoallylic substrate isopentenyl pyrophosphate (IPP) molecules. It is likely that interaction of XcYajQ with XcOPPs may influence the XcOPPs activity. We have expressed and purified XcYajQ and XcOPPs to a hige purity, and used Biacore to measure the affinity between XcYajQ and its two ligands cyclic di-GMP and XcOPPs. XcYajQ is found to exhibit strong affinity toward cyclic di-GMP and XcOPPs with a KD of 0.35µM and 2.76µM, respectively. They are thus good target for structure studies using X-ray crystallography. We also find out that XcYajQ can increase XcOPPs enzyme activity, furthermore, cyclic di-GMP enhance XcOPPs enzyme activity to a higher level by binding to XcYajQ. This dissertation first proves that cyclic di-GMP can indirectly alter XcOPPs enzyme activity by bindind with XcYajQ.