title: CYP3A4 active site volume modification by mutagenesis of leucine 211.
abstract: The leucine 211 --> phenylalanine (L211F) and leucine 211 --> tyrosine (L211Y) mutant forms of cytochrome P450 3A4 have been generated by site-directed mutagenesis and expressed functionally in Escherichia coli. Substrate binding affinities (S50 values) for testosterone and 7-benzyloxy-4-trifluoromethylcoumarin (BFC) were similar for the mutants and wild-type CYP3A4 (49 and 21 microM for L211F, 35 and 20 microM for L211Y, and 33 and 20 microM for the wild type, respectively). For erythromycin, however, the K(m) values determined for the L211F and L211Y mutants were 2.4- and 10.5-fold higher than for the wild type. Furthermore, IC50 values for the inhibition of testosterone 6 beta-hydroxylation by erythromycin and troleandomycin for L211F were 2.4- and 3.7-fold higher, and those for L211Y were 3.4- and 9.2-fold higher than those measured for the wild type. Conversely, small inhibitors, such as diazepam, exhibited no significant difference in IC50 values between the wild type and the L211F and L211Y mutants. It is proposed that large substrates bound in the catalytic center of CYP3A4 with molecular volumes greater than approximately 600 A(3) were less well accommodated in the altered active sites, resulting in lower association energies and increased IC50 values.
authors.affiliation: Physical and Metabolic Science, AstraZeneca R&D Charnwood, Loughborough, United Kingdom. stephen.fowler@pharma.novartis.com
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Fowler
authors.forename: John M
authors.initials: JM
authors.lastname: Taylor
authors.forename: Thomas
authors.initials: T
authors.lastname: Friedberg
authors.forename: C Roland
authors.initials: CR
authors.lastname: Wolf
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Riley
mesh_terms: D019943:Amino Acid Substitution; D014151:Anti-Anxiety Agents / Q000737:chemistry / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001665:Binding Sites / Q000502:physiology; D003374:Coumarins / Q000737:chemistry / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003975:Diazepam / Q000737:chemistry / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004917:Erythromycin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D006900:Hydroxylation / Q000187:drug effects; D007700:Kinetics; D007930:Leucine / Q000235:genetics; D006899:Mixed Function Oxygenases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction / Q000187:drug effects; D013329:Structure-Activity Relationship; D013379:Substrate Specificity / Q000235:genetics; D013739:Testosterone / Q000737:chemistry / Q000378:metabolism; D014217:Troleandomycin / Q000494:pharmacology
chemical_list: C419147:7-benzyloxy-4-trifluoromethylcoumarin; D014151:Anti-Anxiety Agents; D000900:Anti-Bacterial Agents; D003374:Coumarins; D004791:Enzyme Inhibitors; D013739:Testosterone; D004917:Erythromycin; D003577:Cytochrome P-450 Enzyme System; D014217:Troleandomycin; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D007930:Leucine; D003975:Diazepam