title: A single active-site mutation of P450BM-3 dramatically enhances substrate binding and rate of product formation.
abstract: Identifying key structural features of cytochromes P450 is critical in understanding the catalytic mechanism of these important drug-metabolizing enzymes. Cytochrome P450BM-3 (BM-3), a structural and mechanistic P450 model, catalyzes the regio- and stereoselective hydroxylation of fatty acids. Recent work has demonstrated the importance of water in the mechanism of BM-3, and site-specific mutagenesis has helped to elucidate mechanisms of substrate recognition, binding, and product formation. One of the amino acids identified as playing a key role in the active site of BM-3 is alanine 328, which is located in the loop between the K helix and β 1-4. In the A328V BM-3 mutant, substrate affinity increases 5-10-fold and the turnover number increases 2-8-fold compared to wild-type enzyme. Unlike wild-type enzyme, this mutant is purified from E. coli with endogenous substrate bound due to the higher binding affinity. Close examination of the crystal structures of the substrate-bound native and A328V mutant BMPs indicates that the positioning of the substrate is essentially identical in the two forms of the enzyme, with the two valine methyl groups occupying voids present in the active site of the wild-type substrate-bound structure.
authors.affiliation: Department of Chemistry, Sam Houston State University, Huntsville, Texas 77340, United States. Haines@SHSU.edu
authors.forename: Donovan C
authors.initials: DC
authors.lastname: Haines
authors.forename: Amita
authors.initials: A
authors.lastname: Hegde
authors.forename: Baozhi
authors.initials: B
authors.lastname: Chen
authors.forename: Weiqiang
authors.initials: W
authors.lastname: Zhao
authors.forename: Muralidhar
authors.initials: M
authors.lastname: Bondlela
authors.forename: John M
authors.initials: JM
authors.lastname: Humphreys
authors.forename: David A
authors.initials: DA
authors.lastname: Mullin
authors.forename: Diana R
authors.initials: DR
authors.lastname: Tomchick
authors.forename: Mischa
authors.initials: M
authors.lastname: Machius
authors.forename: Julian A
authors.initials: JA
authors.lastname: Peterson
mesh_terms: D000409:Alanine / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009251:NADPH-Ferrihemoprotein Reductase / Q000235:genetics* / Q000378:metabolism; D013379:Substrate Specificity; D014633:Valine / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D003577:Cytochrome P-450 Enzyme System; D009251:NADPH-Ferrihemoprotein Reductase; C052423:flavocytochrome P450 BM3 monoxygenases; D014633:Valine; D000409:Alanine