Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published November 1998 | public
Journal Article

Heme Packing Motifs Revealed by the Crystal Structure of the Tetra-heme Cytochrome c554 from Nitrosomonas europaea

Abstract

Cytochrome c554 (cyt c554), a tetra-heme cytochrome from Nitrosomonas europaea, is an essential component in the biological nitrification pathway. In N. europaea, ammonia is converted to hydroxylamine, which is then oxidized to nitrite by hydroxylamine oxidoreductase (HAO). Cyt c554 functions in the latter process by accepting pairs of electrons from HAO and transferring them to a cytochrome acceptor. The crystal structure of cyt c554 at 2.6 Å resolution shows a predominantly alpha-helical protein with four covalently attached hemes. The four hemes are arranged in two pairs such that the planes of the porphyrin rings are almost parallel and overlapping at the edge; corresponding heme arrangements are observed in other multi-heme proteins. Striking structural similarities are evident between the tetra-heme core of cyt c554 and hemes 3−6 of HAO, which suggests an evolutionary relationship between these redox partners.

Additional Information

© 1998 Nature America Inc. Received 26 June, 1998; accepted 14 September, 1998. We thank J. Hu, L. Joshua-Tor, M. Stowell, D. Cascio, M. Soltis, H. Schindelin, C. Kisker and C. Kielkopf for experimental assistance; C. Drennan and H. Axelrod for critical reading and helpful discussions; K. Matthews and B. Crane for the microspectrophotometery; M. Carrondo for the split Soret cytochrome coordinates; and R. Timkovich for the cytochrome c552 coordinates. This work was supported by an NSF grant to A.B.H and an NIH grant to D.C.R. T.M.I. is supported by an NIH fellowship. The rotation camera facility at SSRL is supported by the NIH and Department of Energy.

Additional details

Created:
August 19, 2023
Modified:
October 19, 2023