Abstract
The partition system played important roles in segregation of chromosome, initiation of sporulation and progression of cell cycle. The ParABS system consisted of two proteins, ParA and ParB, and a parS sequence. In Helicobacter pylori, HpSoj (Hp1139) and HpSpo0J (Hp1138) was putative ParA and ParB proteins, respectively. Except HpSoj is an ATPase; there are few data to support other information. For example how Soj binds DNA and how Soj interacts with HpSpo0J in the HpSoj structure is worth investigating. HpSoj overexpressed and purified with a molecular weight of 29.2 kDa. Whether ATP is present or not, HpSoj was mainly a monomer by size exclusion chromatography. In Electrophoretic mobility shift assay showed that DNA binding activity of ATP-bound HpSoj with pUC19 was stronger than HpSoj. Furthermore, ATP-bound HpSoj had parS-binding activity. The HpSoj-ATP complex crystal was grown using PEG 3350 as a precipitant. Crystal structure of the HpSoj-ATP was determined at 1.9 Å. The HpSoj-ATP complex crystal belongs to P212121 space group with unit cell parameters a=48.1 Å, b=93.3 Å, c=110.9 Å, containing two molecules per asymmetry unit. We try to use the homologous protein as a search model to do the phase calculation by molecular replacement method, and the structure phase determination of HpSoj is still continuing. The three dimensional structure of HpSoj will help us to understand biological function and catalytic mechanisms of HpSoj.