Structure of a water soluble fragment of the ‘Rieske’ iron–sulfur protein of the bovine heart mitochondrial cytochrome bc1 complex determined by MAD phasing at 1.5 å resolution

Abstract

The high-resolution structure supports the proposed coordination pattern involving histidine ligands and provides a basis for a detailed analysis of the spectroscopic and electrochemical properties. As the cluster is located at the tip of the protein, it might come into close contact with cytochrome b. The exposed N epsilon atoms of the histidine ligands of the cluster are readily accessible to quinones and inhibitors within the hydroquinone oxidation (QP) pocket of the bc1 complex and may undergo redox-dependent protonation/deprotonation.

Mechanism of Ubiquinol Oxidation by the bc1 Complex: Role of the Iron Sulfur Protein and Its Mobility

“…A contact to the ISP seen in the density has been modeled as a H-bond between N H-161 of the ISP (one of the [2Fe-2S] ligands) and carbonyl and methoxy oxygens of the stigmatellin ring. A similar H-bonding was suggested previously to account for the effects of stigmatellin on the EPR spectrum and E m value of the ISP (3,38,39). A second ligand is provided by Glu-272 of cyt b, which points into the pocket to form a H-bond from O 1 to the OH of the ring of stigmatellin.…”

“…It seems possible, therefore, that these changes interfered with docking, and inspection of the structure shows that Leu-142 and Gly-143 are at the interfacial surface, with the leucine in close contact with cyt b, but the CR H of glycine facing a small unoccupied volume ( Figure 4B). Brasseur et al (56) noted second-site suppressor strains that restored activity to lethal mutations at Leu-142 in which the modified residue was distant in the tertiary structure and close to the cleavage site in the structure of Iwata et al (3). They speculated that these might indicate an involvement of this region in the correct orientation of the cluster.…”

“…(c) The model in Figure 2 (middle) and the protein and the cluster position 4 (top) are from the structure in the presence of stigmatellin. Although the extrinsic ISP domain was initially located by fitting the structure of Iwata et al (3) to the electron density, the structure of this domain shows some changes due to refinement. However, no major differences from that of the water-soluble fragment are apparent, and the structure did not differ dramatically for the ISP in its different positions.…”

Engineering a Three-cysteine, One-histidine Ligand Environment into a New Hyperthermophilic Archaeal Rieske-type [2Fe-2S] Ferredoxin from Sulfolobus solfataricus

“…It contains the pET28a vector-derived leader nucleotide sequence to facilitate efficient transcription of archaeal genes in E. coli so as to produce a recombinant protein with the N-terminal hexahistidine tag for rapid protein purification. The hexahistidine tag is attached away from the cluster-binding subdomain of ARF and apparently does not disturb its redox site as judged by x-ray crystal structures of several Rieske and Rieske-type protein domains (6,9).…”

X-Ray Structure of Rhodobacter Capsulatus Cytochrome bc1: Comparison with its Mitochondrial and Chloroplast Counterparts

“…capsulatus FeS protein is very similar, to its counterparts in its homologous enzymes, with a base fold and a cluster-bearing fold regions formed of the β-sheets 1, 2 and 3 as described in detail earlier (Iwata et al 1996;Carrell et al 1997). Major differences between the bacterial and mitochondrial FeS proteins include a truncated N-terminus, a 3-residue deletion in the trans-membrane helix, and two insertions in the extrinsic domain (Figure 4).…”