发布时间 :2012-06-13  阅读次数 :591

报告题目:C-di-GMP, PilZ, and Biofilm



报告人:  周三和 教授




报告人网页: http://biochem.nchu.edu.tw/wb_teacher02.asp?cno=1&tno=58


Bacterial type IV pilus (T4P) is a non-flagellar machinery mediating diverse cellular functions, such as surface motility, biofilm formation and pathogenicity. Recent data indicate that T4P biogenesis is initiated via interaction of a non-canonical type II PilZ protein with the FimX and PilB ATPase under high c-di-GMP concentration. However, molecular details of such interactions remain to be elucidated. We now report the hetero-complex crystal structure between a type II PilZ1028 protein and a FimXEAL from Xcc (Xanthomnas campestris pv. campestris) in the presence of c-di-GMP. We demonstrate that c-di-GMP is indispensable for the stable formation of type II XccPilZ1028- XccFimXEAL complex, which is evidenced by a variety of biophysical methods including ITC and gel filtration chromatography. We also show that binding of type II XccPilZ1028 protein induces dimerization of XccFimXEAL domains via a N-terminal helix swapping to form a (XccPilZ1028)2-(XccFimXEAL-c-di-GMP)2 hetero-tetramer complex. In addition, we also observed considerable flexibility for c-di-GMP, which is demonstrated by the discovery of two novel monomeric structures for c-di-GMP  a "bulged" form in the XccFimXEAL-c-di-GMP complex and an "extended but twisted" form in the XccPilZ1028-XccFimXEAL-c-di-GMP complex. Extensive in vitro studies were further carried out using a series of XccPilZ1028 and XccFimXEAL variants to confirm the unique binding modes of c-di-GMP. Altogether, the results represent an important step toward understanding how T4P function is controlled by c-di-GMP in molecular level.

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