Purification, crystallization and preliminary crystallographic analysis of the minor pilin FctB from Streptococcus pyogenes

Abstract

The minor pilin FctB is an integral part of the pilus assembly expressed by Streptococcus pyogenes. Since it is located to the cell wall, it can be hypothesised that it functions as a cell wall anchor for the streptococcal pilus. In order to elucidate its structure, the genes for FctB from the S. pyogenes strains 90/306S and SF370 were cloned for over- expression in Escherichia coli. FctB from strain 90/306S was crystallised by the sitting-drop vapour-diffusion method using sodium citrate as a precipitant. The hexagonal FctB crystals belong to the spacegroups P61 or P65 with the unit-cell parameters a = b = 95.15 Å, c = 100.25 Å and diffracted to 2.9 Å.