Purification, crystallization and preliminary X-ray crystallographic analysis of VCA0593 with a c-di-GMP binding activity in Vibrio cholerae

Many kinds of nucleotides are differentially synthesized and degraded in response to external and internal signaling in bacterial cells. Cyclic di-GMP (c-di-GMP) is ubiquitous bacterial nucleotide secondary signaling molecule, and is involved in virulence, antibiotic resistance, biofilm formation and cell division. VCA0593 was predicted or screened as a c-di-GMP or 5’-phosphguanylyl-(3’,5’)-guanosine binding protein in Vibrio cholerae genome by genome-wide system approaches, suggesting that VCA0593 might be involved in a c-di-GMP-mediated signaling pathway. In this study, the full-length VCA0593 was overexpressed in the E. coli expression system, and successfully crystallized. X-rays were diffracted by the crystals to 1.60 Å resolution, revealing that the crystals belong to space group P2 1 2 1 2, with unit cell parameters a = 68.9, b = 149.0, and c = 58.9 Å. According to cell content analysis, the asymmetric unit was expected to contain two molecules of VCA0593. The molecular replacement was not available due to lack of the homologous models. We are now under way to solve the crystal structure using the anomalous signals from Zn-soaked crystals. The crystal structure would help reveal the function of the protein and its mechanism of action, which could be associated with the pathogenesis of V. cholerae.