Evolutionary comparisons predict that dimerization of human cytochrome P450 aromatase increases its enzymatic activity and efficiency

Lisandra L. Martin, Jessica K. Holien, Dario Mizrachi, C. Jo Corbin, Alan J Conley, Michael W. Parker, Raymond J. Rodgers

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Estrogen is an essential vertebrate hormone synthesized from androgens involving multiple hydroxylations, catalyzed by cytochrome P450 aromatase (P450arom or CYP19) enzymes. Despite their importance, very few comparative studies have been conducted on vertebrate and/or mammalian P450arom enzymes, either structurally or functionally. Here we directly compared the human (h-) and porcine gonadal (pg-) P450arom, as pg-P450arom has very low catalytic efficiency, with a ten-fold higher affinity (Km) for a substrate (androstenedione) and ten-fold reduction in turnover (Vmax). We recombinantly expressed these proteins and compared their interactions on a membrane using a quartz crystal microbalance (QCM) and also with the electron donor protein cytochrome P450 oxidoreductase (CPR). Changes in frequency and dissipation in the QCM supported the h-P450arom forming a homodimer that agreed with the FRET data, but not pg-P450arom. Analysis of the X-ray crystal structure of the h-P450arom suggested a likely site of homo-dimerization and found that certain key interacting residues were not conserved in pg-P450arom. Molecular dynamics simulations provide support for the importance of these residues in homo-dimerization. Here we propose that the lower affinity and higher activity with reduced release of intermediate metabolites by the h-P450arom is as a consequence of its ability to form homodimers. The functional implications of dimerization provide an important mechanistic step in the requirement for efficient aromatization.

Original languageEnglish (US)
Pages (from-to)294-301
Number of pages8
JournalJournal of Steroid Biochemistry and Molecular Biology
Volume154
DOIs
StatePublished - Nov 1 2015

Keywords

  • Cytochrome P450 aromatase
  • Dimerization
  • Estrogen
  • Molecular dynamics
  • proteinprotein interaction

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry
  • Endocrinology
  • Cell Biology
  • Molecular Biology
  • Endocrinology, Diabetes and Metabolism
  • Molecular Medicine

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