Three-dimensional structure of steroid 21-hydroxylase (cytochrome P450 21A2) with two substrates reveals locations of disease-associated variants

J Biol Chem. 2012 Mar 23;287(13):10613-10622. doi: 10.1074/jbc.M111.323501. Epub 2012 Jan 18.


Steroid 21-hydroxylase (cytochrome P450 21A2, CYP21A2) deficiency accounts for ∼95% of individuals with congenital adrenal hyperplasia, a common autosomal recessive metabolic disorder of adrenal steroidogenesis. The effects of amino acid mutations on CYP21A2 activity lead to impairment of the synthesis of cortisol and aldosterone and the excessive production of androgens. In order to understand the structural and molecular basis of this group of diseases, the bovine CYP21A2 crystal structure complexed with the substrate 17-hydroxyprogesterone (17OHP) was determined to 3.0 Å resolution. An intriguing result from this structure is that there are two molecules of 17OHP bound to the enzyme, the distal one being located at the entrance of the substrate access channel and the proximal one bound in the active site. The substrate binding features locate the key substrate recognition residues not only around the heme but also along the substrate access channel. In addition, orientation of the skeleton of the proximal molecule is toward the interior of the enzyme away from the substrate access channel. The 17OHP complex of CYP21A2 provides a good relationship between the crystal structure, clinical data, and genetic mutants documented in the literature, thereby enhancing our understanding of congenital adrenal hyperplasia. In addition, the location of certain CYP21A2 mutations provides general understanding of structure/function relationships in P450s.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • 17-alpha-Hydroxyprogesterone / chemistry*
  • 17-alpha-Hydroxyprogesterone / metabolism
  • Adrenal Hyperplasia, Congenital / enzymology*
  • Adrenal Hyperplasia, Congenital / genetics
  • Animals
  • Binding Sites
  • Cattle
  • Crystallography, X-Ray
  • Humans
  • Mutation*
  • Steroid 21-Hydroxylase / chemistry*
  • Steroid 21-Hydroxylase / genetics
  • Steroid 21-Hydroxylase / metabolism
  • Structure-Activity Relationship


  • 17-alpha-Hydroxyprogesterone
  • Steroid 21-Hydroxylase

Associated data

  • PDB/3QZ1