Structure of cytochrome c551 from Pseudomonas aeruginosa refined at 1.6 Å resolution and comparison of the two redox forms

Amino acid sequence, haem-iron co-ordination geometry and functional properties of mitochondrial and bacterial c-type cytochromes

“…In all known cytochrome c sequences the axial histidine and methionine (His 18 and Met 80 in Table 1) are the only strictly conserved amino-acid residues in the primary structure (Meyer & Kamen, 1982;Schwartz & Dayhoff, 1976;Dayhoff & Barker, 1978) besides Cys 17. The present paper surveys the available data on the haem-iron co-ordination geometry in class I cytochromes (Senn, 1983;Senn & Wuthrich, 1983 a, b, c;Senn, Keller & Wuthrich, 1980;Senn, Eugster & Wuthrich, 1983 a;Senn et al 1983ft;Senn, Billiter & Wuthrich, 1984 a;Senn, Bohme & Wuthrich, 19846;Senn, Cusanovich & Wuthrich, 1984c;Keller, Picot & Wuthrich, 1979Ulrich, Krogmann & Markley, 1982;Salemme et al 1973;Takano & Dickerson, 19810,6;Matsuura, Takano & Dickerson, 1982;Timkovich 1979) and investigates possible correlations with the amino acid sequence and functional properties. The proteins studied (Table 1) were selected from a broad range of eucaryotic and bacterial organisms so that the investigations could be extended to phylogenetic information on the haem-iron co-ordination geometry and the haem c electronic structure.…”

“…1 A). In the cytochromes c-551 from P. aeruginosa (Senn et al 1980(Senn et al , 1984c Properties of c-type cytochromes 115 Matsuura et al 1982), P. mendocina (Senn & Wiithrich, 19836), P. stutzeri (Senn & Wiithrich, 19836) and Rps. gelatinosa (Senn & Wiithrich, 1983 a) the axial methionine has S chirality at the ironbound sulphur and the methionine side chain is bent, so that C^H 2 is closer to the e-methyl group than C y H 2 .…”

“…An important feature in determining the axial histidine orientation appears to be the presence of an H-bond between the N t H of the axial imidazole ring and the C = O group of Pro 30 (Takano & Dickerson, 1981a;Salemme et al 1973;Matsuura et al 1982) (Table 1). From the observation that the protein sequences of all mitochondrial and most of the bacterial c-type cytochromes show a conserved proline at position 30 (Table 1) (Bartsch 1978;Schwartz & DayhofT, 1976; I2O H. SENN AND K. WUTHRICH Dayhoff & Barker, 1978;Dickerson, 1980 a), we infer that this homologous position assists in conservation of the spatial orientation of the axial histidine.…”

“…In both species the edge of the pyrrole ring II is accessible on the surface. Because of extensive deletions in the polypeptide chain of P. aeruginosa cytochrome c-551 (Table 1) the edge of pyrrole ring III is also accessible on the protein surface of this species (Matsuura et al 1982).…”

“…The apparent free energy of electron transfer would be lowered as a result of this conformation change. Experimental support for the potential of c-type cytochromes to adopt such intermediate structures comes from single crystal X-ray studies (Takano & Dickerson, 19810,6;Matsuura et al 1982), chemical modification (Ferguson-Miller et al 1979;Osheroff et al 1979Osheroff et al , 1980Koppenol & Margoliash, 1982) and NMR studies (Moore et al 1982;Senn et al 1983 a, 19846;Keller & Wiithrich, 1981). These studies also show that the biologically interacting surface of the globular molecule lies close to the axial methionine and is conformationally rather flexible.…”