Crystal structures of cytochrome P450 105P1 from Streptomyces avermitilis: conformational flexibility and histidine ligation state

J Bacteriol. 2009 Feb;191(4):1211-9. doi: 10.1128/JB.01276-08. Epub 2008 Dec 12.


The polyene macrolide antibiotic filipin is widely used as a probe for cholesterol in biological membranes. The filipin biosynthetic pathway of Streptomyces avermitilis contains two position-specific hydroxylases, C26-specific CYP105P1 and C1'-specific CYP105D6. In this study, we describe the three X-ray crystal structures of CYP105P1: the ligand-free wild-type (WT-free), 4-phenylimidazole-bound wild-type (WT-4PI), and ligand-free H72A mutant (H72A-free) forms. The BC loop region in the WT-free structure has a unique feature; the side chain of His72 within this region is ligated to the heme iron. On the other hand, this region is highly disordered and widely open in WT-4PI and H72A-free structures, respectively. Histidine ligation of wild-type CYP105P1 was not detectable in solution, and a type II spectral change was clearly observed when 4-phenylimidazole was titrated. The H72A mutant showed spectroscopic characteristics that were almost identical to those of the wild-type protein. In the H72A-free structure, there is a large pocket that is of the same size as the filipin molecule. The highly flexible feature of the BC loop region of CYP105P1 may be required to accept a large hydrophobic substrate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism*
  • Crystallization
  • Cytochrome P-450 Enzyme System / chemistry
  • Cytochrome P-450 Enzyme System / metabolism*
  • Filipin / chemistry
  • Filipin / metabolism
  • Histidine / chemistry*
  • Models, Molecular
  • Molecular Structure
  • Mutagenesis, Site-Directed
  • Mutation
  • Protein Conformation
  • Streptomyces / enzymology*


  • Bacterial Proteins
  • Histidine
  • Filipin
  • Cytochrome P-450 Enzyme System