Structural and enzymatic analysis of MshA from Corynebacterium glutamicum: substrate-assisted catalysis.
The glycosyltransferase termed MshA catalyzes the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to 1-L-myo-inositol-1-phosphate in the first committed step of mycothiol biosynthesis. The structure of MshA from Corynebacterium glutamicum was determined both in the absence of substrates and in a complex with UDP and 1-L-myo-inositol-1-phosphate. MshA belongs to the GT-B structural family whose members have a two-domain structure with both domains exhibiting a Rossman-type fold. Binding of the donor sugar to the C-terminal domain produces a 97 degrees rotational reorientation of the N-terminal domain relative to the C-terminal domain, clamping down on UDP and generating the binding site for 1-L-myo-inositol-1-phosphate. The structure highlights the residues important in binding of UDP-N-acetylglucosamine and 1-L-myo-inositol-1-phosphate. Molecular models of the ternary complex suggest a mechanism in which the beta-phosphate of the substrate, UDP-N-acetylglucosamine, promotes the nucleophilic attack of the 3-hydroxyl group of 1-L-myo-inositol-1-phosphate while at the same time promoting the cleavage of the sugar nucleotide bond.
Vetting
Matthew W
MW
Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA. vetting@aecom.yu.edu
Frantom
Patrick A
PA
Blanchard
John S
JS
D000117:Acetylglucosamine / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites / Q000502:physiology; D002384:Catalysis; D048230:Corynebacterium glutamicum / Q000201:enzymology*; D016695:Glycosyltransferases / Q000737:chemistry* / Q000378:metabolism; D007295:Inositol Phosphates / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D017510:Protein Folding; D017434:Protein Structure, Tertiary / Q000502:physiology; D040681:Structural Homology, Protein; D014530:Uridine Diphosphate / Q000737:chemistry* / Q000378:metabolism
D007295:Inositol Phosphates; C002647:inositol 1-phosphate; D014530:Uridine Diphosphate; D016695:Glycosyltransferases; D000117:Acetylglucosamine