Structural Studies of Isopropylmalate Synthase from Mycobacterium Tuberculosis.

The crystal structure of the laminin-binding protein Lbp (Spy2007) of Streptococcus pyogenes has been determined to 2.45 Å resolution.According to recent studies, Lbp mediates adhesion of the major human pathogens S. pyogenes and S. agalactiae to the human basal lamina glycoprotein laminin.It has been shown to be essential in in vitro models of adhesion and invasion.In this study, lbp from S. pyogenes strain M1 was cloned, expressed in E. coli as a (His)6tagged protein and purified by IMAC.Recombinant Lbp yielded crystals belonging to the monoclinic space group P21 and of good diffraction quality.The structure of Lbp to a resolution of 2.45 Å was solved by molecular replacement using an ensemble of search models from homologous proteins and was refined to an Rcryst of 18.6 % and Rfree of 24.7 %.The structure consists of a long helical backbone connecting two lobes which enclose a cobalt ion in a characteristic histidine/glutamate metal binding site.It is largely similar to that of homologous proteins, which are implicated in metal transport, but is among the first bacterial laminin-binding proteins to be determined.The crystal structure of Lbp will allow further investigations into the molecular basis of laminin-binding by human pathogens and give new insight into host-pathogen interactions.As Lbp is immunogenic and conserved in all S. pyogenes strains, its structure may guide development of an efficient vaccine.