Expression, purification, crystallization and structure determination of the N terminal domain of Fhb, a factor H binding protein from Streptococcus suis

摘要

Fhb is a surface virulence protein from Streptococcus suis, which could aid bacterial evasion of host innate immune defense by recruiting complement regulator factor H to inactivate C3b deposited on bacterial surface in blood. Here we successfully expressed and purified the N terminal domain of Fhb (N-Fhb) and obtained crystals of the N-Fhb by sitting-drop vapor diffusion method with a resolution of 1.50 angstrom. The crystals belong to space group C2 with unit cell parameters a = 127.1 angstrom, b = 773 angstrom, c = 131.6 angstrom, alpha = 90 degrees, beta = 115.9 degrees, gamma = 90 degrees. The structure of N-Fhb was determined by SAD method and the core structure of N-Fhb is a 13 sandwich. We speculated that binding of Fhb to human factor H may be mainly mediated by surface amino acids with negative charges. (C) 2015 Elsevier Inc. All rights reserved.