High-resolution structures of the oxidized and reduced states of cytochrome c554 from Nitrosomonas europaea

J Biol Inorg Chem. 2001 Apr;6(4):390-7. doi: 10.1007/s007750100213.


Cytochrome c554 (cyt c554) is a tetra-heme cytochrome involved in the oxidation of NH3 by Nitrosomonas europaea. The X-ray crystal structures of both the oxidized and dithionite-reduced states of cyt c554 in a new, rhombohedral crystal form have been solved by molecular replacement, at 1.6 A and 1.8 A resolution, respectively. Upon reduction, the conformation of the polypeptide chain changes between residues 175 and 179, which are adjacent to hemes III and IV. Cyt c554 displays conserved heme-packing motifs that are present in other heme-containing proteins. Comparisons to hydroxylamine oxidoreductase, the electron donor to cyt c554, and cytochrome c nitrite reductase, an enzyme involved in nitrite ammonification, reveal substantial structural similarity in the polypeptide chain surrounding the heme core environment. The structural determinants of these heme-packing motifs extend to the buried water molecules that hydrogen bond to the histidine ligands to the heme iron. In the original structure determination of a tetragonal crystal form, a cis peptide bond between His129 and Phe130 was identified that appeared to be stabilized by crystal contacts. In the rhombohedral crystal form used in the present high-resolution structure determination, this peptide bond adopts the trans conformation, but with disallowed angles of phi and psi.

Publication types

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

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Crystallography, X-Ray
  • Cytochrome c Group / chemistry*
  • Cytochrome c Group / metabolism*
  • Heme / metabolism
  • Histidine / chemistry
  • Models, Molecular
  • Molecular Sequence Data
  • Nitrosomonas / enzymology*
  • Oxidation-Reduction
  • Phenylalanine / chemistry
  • Protein Conformation
  • Protein Folding


  • Cytochrome c Group
  • cytochrome c553
  • Heme
  • Phenylalanine
  • Histidine
  • cytochrome C-552

Associated data

  • PDB/1BVB