Structure and catalytic cycle of beta-1,4-galactosyltransferase.
Beta-1,4-galactosyltransferase-1, a housekeeping enzyme that functions in the synthesis of glycoconjugates, has two flexible loops, one short and one long. Upon binding a metal ion and UDP-galactose, the loops change from an open to a closed conformation, repositioning residues to lock the ligands in place. Residues at the N-terminal region of the long loop form the metal-binding site and those at the C-terminal region form a helix, which becomes part of the binding site for the oligosaccharide acceptor; the remaining residues cover the bound sugar-nucleotide. After binding of the oligosaccharide acceptor and transfer of the galactose moiety, the product disaccharide unit is ejected and the enzyme returns to the open conformation, repeating the catalytic cycle.
Ramakrishnan
Boopathy
B
Structural Glycobiology Section, Laboratory of Experimental and Computational Biology, Center for Cancer Research, NCI-Frederick, MD 21702, USA.
Boeggeman
Elizabeth
E
Ramasamy
Velavan
V
Qasba
Pradman K
PK
D002384:Catalysis; D007788:Lactose Synthase / Q000737:chemistry / Q000378:metabolism; D008670:Metals / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D009237:N-Acetyllactosamine Synthase / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation
D008670:Metals; D007788:Lactose Synthase; D009237:N-Acetyllactosamine Synthase