Abstract
Helicobacter pylori is a micro-aerophilic Gram-negative bacillus. It has 4~6 flagella enables the bacterium to have the high motion ability. There are probably 50% population to be infected by the H. pylori all over the world. The infection of the H. pylori leads to serious disease such as duodenal or gastric ulcer, gastric adenocarcinoma, or mucosa-associated lymphoid tissue lymphoma. In order to realize the acute disease cause by the bacteria, we selected the H. pylori to be the target of structural genomics project. The topic of my research is about the structural and functional of HP1492. Iron-sulfur proteins are distributed among various organisms and are known to play important physiological roles not only in electron transfer or metabolic reactions but also in gene regulation. Although cellular functions and enzymatic reactions of many iron-sulfur proteins have been extensively studied, molecular mechanisms involved in the assembly of the iron-sulfur cluster into the polypeptides still remain unclear. In our study, the HP1492 NifU homolog shares high sequence homology with the carboxyl-terminal domain and contains the conserved Cys-X-X-Cys motif of A. vinelandii NifU. In order to understand the structure and the function of HP1492. We designed a succession of experiment. We used the Circular Dichroism to know the Tm value of HP1492 may reach as high as 82 ℃, the Cm value also reaches as high as 3.7M Urea. This result shows that HP1492 has high stability. We study three Cys of HP1492 by site-directed mutagenesis. We found that all of these three Cys play an important role in binding with Fe. Finally in the structural study, the high population of the homodimer make the structural study by NMR be more difficult. Site-directed mutagenesis of C79A reducing the formation of homodimer. The spectrums of HSQC and the stability detected by CD are similar to wild type HP1492. Thus site-directed mutagenesis of C79A may be used for the structural study.