Crystal Structure And Function Of VibB And Its Interaction With VibD

In order to survive in iron deficient environment, microorganisms have developed some complex strategies to obtain ferrous. One of those is to secrete a kind of small molecule name siderophore, and the expression of the genes synthesizing siderophores are regulated by Fur box. The siderophores will chelate iron in high efficiency after released to the environment. When siderophores have binded iron, they will be transported into plasmic of microorganisms by a series of transport proteins including outer membrane receptor proteins, periplasmic proteins and inner membrane ABC transport proteins.Vibriobactin is a kind of siderophore secreted by Vibrio cholerae. To synthesize vibriobactin, proteins of VibA, VibB, VibC, VibD, VibE, VibF and VibH are needed. VibB is a bifunction enzyme, in one hand, it can catalyze hydrolyzing of one intermediate-isochorismate acting as a vinyl-ether hydrolase, and for now, the catalyzing process of isochorismatase is still not clear; In other hand, VibB can act as a carrier protein, which will obtain the function to transport DHB after activated by a phosphopantetheinyl transferase - VibD. However, there are different opinions about the mechanisms of water and the metal ion in activation center.Our purpose is to understand the biochemical function of VibB and the mechanism that how VibB is chemically modified by VibD through the 3-D structure of VibB and VibB-VibD complex. Recently, crystal structure of VibB has been solved, including domain of VibB-ISC and the complex of VibB-ISC-isochorismate. We have better understandings about the catalyzing center of isochorismatase after analyzing the structure of VibB-ISC and its complex with substrate. Some new hypothesizes have been raised, and which have been confirmed by experiments.