crystal structure of spy0129, a streptococcus pyogenes class b sortase involved in pilus assemblyspy0129晶体结构,酿脓链球菌b类sortase参与纤毛组装.pdfVIP

Crystal Structure of Spy0129, a Streptococcus pyogenes Class B Sortase Involved in Pilus Assembly 1,2¤a ´ 1,2¤b 1,3 1,2 Hae Joo Kang , Fasseli Coulibaly , Thomas Proft , Edward N. Baker * 1 Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand, 2 School of Biological Sciences, University of Auckland, Auckland, New Zealand, 3 School of Medical Sciences, University of Auckland, Auckland, New Zealand Abstract Sortase enzymes are cysteine transpeptidases that mediate the covalent attachment of substrate proteins to the cell walls of Gram-positive bacteria, and thereby play a crucial role in virulence, infection and colonisation by pathogens. Many cell- surface proteins are anchored by the housekeeping sortase SrtA but other more specialised sortases exist that attach sub- sets of proteins or function in pilus assembly. The sortase Spy0129, or SrtC1, from the M1 SF370 strain of Streptococcus pyogenes is responsible for generating the covalent linkages between the pilin subunits in the pili of this organism. The ˚ crystal structure of Spy0129 has been determined at 2.3 A resolution (R = 20.4%, Rfree = 26.0%). The structure shows that Spy0129 is a class B sortase, in contrast to other characterised pilin polymerases, which belong to class C. Spy0129 lacks a flap believed to function in substrate recognition in class C enzymes and instead has an elaborated b6/b7 loop. The two independent Spy0129 molecules in the crystal show differences in the positions and orientations of the catalytic Cys and His residues, Cys221 and His126, correlated with movements of the b7/b8 and b4/b5 loops that