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Structural and functional characterization of ATP binding HP1026 - Helicobacter pylori heat shock protein

Helicobacter pylori is a gram negative microaerophilic bacterium that colonizes the human gastric mucosa. It is considered as a principal cause of chronic gastric diseases such as gastric and duodenal ulcers and as a possible trigger for the development of adenocarcinoma. H. pylori enables the successful infection and adaption to the extreme gastric environment by the chaperons (HrcA, HspR) and heat shock proteins (HSPs) which are involved in regulation of urease activity and adhesion to epithelial cells. The HSPs of H. pylori are organised in three multicistronic operons, transcriptionally controlled by three upstream promoters (Pgro, Phrc, Pcbp). In this study we focused on structural and functional characterization of HP1026 protein, which is part of one of the heat shock operon controlled under the HspR regulator. We performed cloning, purification, biophysical characterization and crystallization studies. ATP hydrolysis assay showed that HP1026 possesses an ATPase activity within kinetics parameters as follows: Km= 344 uM, vmax= 0.6019 uM s-1, kcat= 0.02 s-1. Gel filtration profile indicated the presence of dimeric species in the solution for both Apo- and ATP-gamma-S treated HP1026, so no oligomerization step was observed after the addition of ATP-gamma-S. CD analysis showed that alpha-helixes are presented as major secondary structure elements. A good quality of sample for the crystallization studies was confirmed by the DLS experiment (PDI < 0.3) thus crystallization trials were carried out for Apo-, ATP-gamma-S- and SeMET- HP1026 by the sitting drop vapour diffusion method using an automated crystallization platform (Oryx 8 robot). The hexagonal shaped crystals were grown in a week at 293(2) K.

H. pylori; HP1026; ATPase activity; crystallization

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