Crystal structure of substrate-free Pseudomonas putida cytochrome P-450

Biochemistry. 1986 Sep 9;25(18):5314-22. doi: 10.1021/bi00366a049.


The crystal structure of Pseudomonas putida cytochrome P-450cam in the substrate-free form has been refined at 2.20-A resolution and compared to the substrate-bound form of the enzyme. In the absence of the substrate camphor, the P-450cam heme iron atom is hexacoordinate with the sulfur atom of Cys-357 providing one axial heme ligand and a water molecule or hydroxide ion providing the other axial ligand. A network of hydrogen-bonded solvent molecules occupies the substrate pocket in addition to the iron-linked aqua ligand. When a camphor molecule binds, the active site waters including the aqua ligand are displaced, resulting in a pentacoordinate high-spin heme iron atom. Analysis of the Fno camphor - F camphor difference Fourier and a quantitative comparison of the two refined structures reveal that no detectable conformational change results from camphor binding other than a small repositioning of a phenylalanine side chain that contacts the camphor molecule. However, large decreases in the mean temperature factors of three separate segments of the protein centered on Tyr-96, Thr-185, and Asp-251 result from camphor binding. This indicates that camphor binding decreases the flexibility in these three regions of the P-450cam molecule without altering the mean position of the atoms involved.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Crystallization
  • Cytochrome P-450 Enzyme System / isolation & purification*
  • Dithiothreitol
  • Models, Molecular
  • Protein Conformation
  • Pseudomonas / metabolism*
  • X-Ray Diffraction


  • Cytochrome P-450 Enzyme System
  • Dithiothreitol