Abstract
The cell binding factor 2 of Helicobacter pylori (HpCBF2) is a virulence factor and transactivates epidermal growth factor receptor (EGFR) through TLR4 in gastric epithelial cells and lead to abnormal cell proliferation. HpCBF2 catalyzed cis-trans isomerization of proline peptide bond on oligopeptide. HpCBF2 also plays an important role in outer membrane protein maturation and may participate in protein folding at the rate-limiting step. HpCBF2 has been overexpressed and isolated with a molecular weight of 31,910 Da. HpCBF2 functions as a dimer. The isomerization activity of HpCBF2 was performed by a coupling enzyme assay using Suc-AAPF-pNA as a substrate analog. The catalytic efficiency (kcat/Km) of HpCBF2 was calculated as 238 ± 7.2 mM−1s−1. HpCBF2 was crystallized by means of Jeffamine M-600 as a precipitant. HpCBF2 crystal belongs to P3121 space group with cell parameters a = 61.7 Å, b = 61.7 Å, c = 367.0 Å, at 2.6 Å resolution. There are two molecules per asymmetric unit with Vm of 3.16 Å3Da−1 and solvent content of 61%. The crystal structure of HpCBF2 was determined by the single anomalous dispersion (SAD) method via the selenium derivative. The overall structure of HpCBF2 contains a PPIase domain and a chaperone domain. The PPIase domain is composed of three β strands and α helices and the substrate-binding pocket consists of six conserved residues, His131, Asp169, Leu181, Met189, Phe193, Phe215 and His217. The chaperone domain is composed of four α helices and two chaperone domains build up a domain-swapped architecture. These structural results provide a understanding of the biological function of HpCBF2 and suggest the possibility of the drug design on HpCBF2 as well as the potential alinic application in H.pylori.