1C52

THERMUS THERMOPHILUS CYTOCHROME-C552: A NEW HIGHLY THERMOSTABLE CYTOCHROME-C STRUCTURE OBTAINED BY MAD PHASING

Summary for 1C52

• Entry DOI: 10.2210/pdb1c52/pdb
• Descriptor: CYTOCHROME-C552, PROTOPORPHYRIN IX CONTAINING FE (3 entities in total)
• Functional Keywords: electron transport protein, cytochrome-c552, mad, thermostability
• Biological source: Thermus thermophilus
• Total number of polymer chains: 1
• Total formula weight: 14811.06

Authors

Than, M.E.,Hof, P.,Huber, R.,Bourenkov, G.P.,Bartunik, H.D.,Buse, G.,Soulimane, T. (deposition date: 1997-06-23, release date: 1998-06-24, Last modification date: 2024-10-23)

Primary citation

Than, M.E.,Hof, P.,Huber, R.,Bourenkov, G.P.,Bartunik, H.D.,Buse, G.,Soulimane, T.
Thermus thermophilus cytochrome-c552: A new highly thermostable cytochrome-c structure obtained by MAD phasing.
J.Mol.Biol., 271:629-644, 1997

PubMed Abstract: The three-dimensional structure of cytochrome-c552 from Thermus thermophilus has been determined by the multiple anomalous dispersion technique using synchrotron radiation and refined to a resolution of 1.28 A. Data collection at 90 K and the recording of three data sets (f'-minimum: 7125 eV, f"-maximum: 7138 eV and reference for scaling: 10,077 eV) resulted in an initial electron density of very high quality at 2.1 A, which was readily interpretable for model building. The model was refined to an R value of 19.1% (Rfree=22.4%) at 1.28 A resolution using a fourth data set collected at a photon energy of 11,810 eV. Comparison of this thermophilic cytochrome with its mesophilic mitochondrial or bacterial counterparts reveals significant structural differences which are discussed with respect to their importance for thermostability and binding between this cytochrome and its corresponding ba3-oxidase. Amino acid sequence similarities to other class I cytochromes are very weak and entirely limited to the region around the CXXCH motif close to the N terminus. The N-terminal two-thirds of cytochrome-c552 cover spatial regions around the heme prosthetic group that are similar to those observed for other cytochromes. The actual secondary structural elements that are responsible for that shielding do not, however, correlate well to other structures. Only the N-terminal helix (containing the heme binding cysteine residues) aligns reasonably well with other class I cytochromes. The most striking differences that distinguish the present structure from all other class I cytochromes is the C-terminal one-third of the molecule that wraps around the remainder of the structure as a stabilizing clamp, the existence of an extended beta-sheet covering one edge of the heme and the lack of any internal water molecule.

PubMed: 9281430
DOI: 10.1006/jmbi.1997.1181

Experimental method

X-RAY DIFFRACTION (1.28 Å)