High-resolution structures of the oxidized and reduced states of cytochrome c554 from Nitrosomonas europaea.Iverson, T.M., Arciero, D.M., Hooper, A.B., Rees, D.C.
(2001) J Biol Inorg Chem 6: 390-397
- PubMed: 11372197
- DOI: https://doi.org/10.1007/s007750100213
- Primary Citation of Related Structures:
- PubMed Abstract:
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.
Division of Chemistry and Chemical Engineering and Howard Hughes Medical Institute, MC 147-75 CH, California Institute of Technology, Pasadena, CA 91125, USA.