Progress in Biochemistry and Biophysics 2005;32(3):217-220

Protein Preparation, Crystallization and Preliminary X-ray Crystallographic Analysis of Smu.260 From Streptococcus mutans--a Cariogenic Dental Pathogen

Xiaoyan ZHANG ; Wei MI ; Yanfeng ZHOU ; Xiangyu LIU ; Lanfen LI ; Yuhe LIANG ; Shicheng WEI ; Xiaodong SU

Keywords

Streptococcus mutans; dental caries; Smu.260; protein crystallography

Country

China

Language

Chinese

Abstract

Smu. 260 encodes a putative protein of 200 residues in Streptococcus mutans, a primary pathogen for human dental caries. Smu. 260 was cloned into expression vector pET28a and expressed in good amount trom the E. coli strain BL21 (DE3). Smu.260 protein was purified to homogeneity in a two-step procedure of Ni2+ chelating and size exclusion chromatography. The purified protein exists in two forms, a dimer form about 46 ku with yellow color and a tetramer form without apparent color. Crystals were obtained from the dimer protein by hanging-drop vapor-diffusion method. The crystals diffracted to about 2.3 A resolution and belong to orthorhombic space group P212121 with cell dimensions of a = 89.88A, b = 90.91 A, c = 105.17 A. The asymmetric unit is expected to contain two dimers with solvent content of 53%.