1cgo
From Proteopedia
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CYTOCHROME C'
Overview
The three-dimensional structures of two cytochromes c' have been, determined in order to analyse the common features of proteins of this, family and their relationship with other four-helix bundle structures. The, structure of cytochrome c' from Alcaligenes sp was determined by molecular, replacement supplemented with the iron anomalous scattering and the use of, a single isomorphous heavy-atom derivative, and was refined using, synchrotron data to 1.8 A resolution. The final model, comprising 956, protein atoms (one monomer) and 89 water molecules, has a final R value of, 0.188 for all data in the range 20.0-1.8 A resolution (14 673, reflections). The structure of the cytochrome c' from Alcaligenes, denitrificans is isomorphous and essentially identical (r.m.s. deviation, for all atoms 0.36 A). Although its amino-acid sequence has not been, determined chemically, only four differences from that of Alcaligenes sp, cytochrome c' were identified by the X-ray analysis. The final model for, Alcaligenes denitrificans cytochrome c', comprising 953 protein atoms and, 75 water molecules, gave a final R factor of 0.167 for all data in the, range 20.0-2.15 A (8220 reflections). The cytochrome c' monomer forms a, classic four-helix bundle, determined by the packing of hydrophobic side, chains around the enclosed haem group. There are very few cross-linking, hydrogen bonds between the helices, the principal side-chain hydrogen, bonding involving one of the haem propionates and a conserved Arg residue., The cytochrome c' dimer is created by a crystallographic twofold axis., Monomer-monomer contacts primarily involve the two A helices, with size, complementarity of side chains in a central solvent-excluded portion of, the interface and hydrogen bonding at the periphery. Both species have a, pyroglutamic acid N-terminal residue. The haem iron is five-coordinate, 0.32 A out of the haem plane towards the fifth ligand, His120. The unusual, magnetic properties of the Fe atom may be linked to a conserved basic, residue, Arg124, adjacent to His120.
About this Structure
1CGO is a Single protein structure of sequence from Alcaligenes sp. with HEM as ligand. Full crystallographic information is available from OCA.
Reference
Three-dimensional structure of cytochrome c' from two Alcaligenes species and the implications for four-helix bundle structures., Dobbs AJ, Anderson BF, Faber HR, Baker EN, Acta Crystallogr D Biol Crystallogr. 1996 Mar 1;52(Pt 2):356-68. PMID:15299707
Page seeded by OCA on Tue Nov 20 12:26:09 2007
