Substrate-induced closure of the flap domain in the ternary complex structures provides insights into the mechanism of catalysis by 3-hydroxy-3-methylglutaryl-CoA reductase.
3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase is the rate-limiting enzyme and the first committed step in the biosynthesis of cholesterol in mammals. We have determined the crystal structures of two nonproductive ternary complexes of HMG-CoA reductase, HMG-CoA/NAD+ and mevalonate/NADH, at 2.8 A resolution. In the structure of the Pseudomonas mevalonii apoenzyme, the last 50 residues of the C terminus (the flap domain), including the catalytic residue His381, were not visible. The structures of the ternary complexes reported here reveal a substrate-induced closing of the flap domain that completes the active site and aligns the catalytic histidine proximal to the thioester of HMG-CoA. The structures also present evidence that Lys267 is critically involved in catalysis and provide insights into the catalytic mechanism.
Tabernero
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Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
Bochar
D A
DA
Rodwell
V W
VW
Stauffacher
C V
CV
D000595:Amino Acid Sequence; D004789:Enzyme Activation; D006903:Hydroxymethylglutaryl CoA Reductases / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011549:Pseudomonas; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D006903:Hydroxymethylglutaryl CoA Reductases