title: Human cytochrome P450 17A1 conformational selection: modulation by ligand and cytochrome b5.
abstract: Crystallographic studies of different membrane cytochrome P450 enzymes have provided examples of distinct structural conformations, suggesting protein flexibility. It has been speculated that conformational selection is an integral component of substrate recognition and access, but direct evidence of such substate interconversion has thus far remained elusive. In the current study, solution NMR revealed multiple and exchanging backbone conformations for certain structural features of the human steroidogenic cytochrome P450 17A1 (CYP17A1). This bifunctional enzyme is responsible for pregnenolone C17 hydroxylation, followed by a 17,20-lyase reaction to produce dehydroepiandrosterone, the key intermediate in human synthesis of androgen and estrogen sex steroids. The distribution of CYP17A1 conformational states was influenced by temperature, binding of these two substrates, and binding of the soluble domain of cytochrome b5 (b5). Notably, titration of b5 to CYP17A1·pregnenolone induced a set of conformational states closely resembling those of CYP17A1·17α-hydroxypregnenolone without b5, providing structural evidence consistent with the reported ability of b5 to selectively enhance 17,20-lyase activity. Solution NMR thus revealed a set of conformations likely to modulate human steroidogenesis by CYP17A1, demonstrating that this approach has the potential to make similar contributions to understanding the functions of other membrane P450 enzymes involved in drug metabolism and disease states.
authors.affiliation: From the Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045 and.
authors.forename: D Fernando
authors.initials: DF
authors.lastname: Estrada
authors.affiliation: From the Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045 and.
authors.forename: Andria L
authors.initials: AL
authors.lastname: Skinner
authors.affiliation: the Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas 66047 laurencj@ku.edu.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Laurence
authors.affiliation: From the Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045 and eescott@ku.edu.
authors.forename: Emily E
authors.initials: EE
authors.lastname: Scott
mesh_terms: D000736:Androstenes; D000737:Androstenols / Q000378:metabolism / Q000494:pharmacology; D065607:Cytochrome P-450 Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D015786:Cytochromes b5 / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation / Q000187:drug effects; D013254:Steroid 17-alpha-Hydroxylase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D000736:Androstenes; D000737:Androstenols; D065607:Cytochrome P-450 Enzyme Inhibitors; D015786:Cytochromes b5; C501892:CYP17A1 protein, human; D013254:Steroid 17-alpha-Hydroxylase; C089740:abiraterone
keywords: Cytochrome P450; Cytochrome b5; Membrane Proteins; NMR; Protein Structure; Steroidogenesis