Structural analysis of the sialyltransferase CstII from Campylobacter jejuni in complex with a substrate analog.
Sialic acid terminates oligosaccharide chains on mammalian and microbial cell surfaces, playing critical roles in recognition and adherence. The enzymes that transfer the sialic acid moiety from cytidine-5'-monophospho-N-acetyl-neuraminic acid (CMP-NeuAc) to the terminal positions of these key glycoconjugates are known as sialyltransferases. Despite their important biological roles, little is understood about the mechanism or molecular structure of these membrane-associated enzymes. We report the first structure of a sialyltransferase, that of CstII from Campylobacter jejuni, a highly prevalent foodborne pathogen. Our structural, mutagenesis and kinetic data provide support for a novel mode of substrate binding and glycosyl transfer mechanism, including essential roles of a histidine (general base) and two tyrosine residues (coordination of the phosphate leaving group). This work provides a framework for understanding the activity of several sialyltransferases, from bacterial to human, and for the structure-based design of specific inhibitors.
Chiu
Cecilia P C
CP
Department of Biochemistry and Molecular Biology, University of British Columbia, 2146 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada.
Watts
Andrew G
AG
Lairson
Luke L
LL
Gilbert
Michel
M
Lim
Daniel
D
Wakarchuk
Warren W
WW
Withers
Stephen G
SG
Strynadka
Natalie C J
NC
D001483:Base Sequence; D016123:Campylobacter jejuni / Q000201:enzymology*; D003569:Cytidine Monophosphate N-Acetylneuraminic Acid / Q000378:metabolism*; D017931:DNA Primers; D007700:Kinetics; D008958:Models, Molecular; D011487:Protein Conformation; D012799:Sialyltransferases / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity
D017931:DNA Primers; D003569:Cytidine Monophosphate N-Acetylneuraminic Acid; D012799:Sialyltransferases