Structure of a thermophilic cyanobacterialb₆f-type Rieske protein

Abstract

The `Rieske protein' PetC is one of the key subunits of the cytochrome b(6)f complex. Its Rieske-type [2Fe-2S] cluster participates in the photosynthetic electron-transport chain. Overexpression and careful structure analysis at 2.0 Å resolution of the extrinsic soluble domain of PetC from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 enabled in-depth spectroscopic and structural characterization and suggested novel structural features. In particular, both the protein structure and the positions of the internal water molecules unexpectedly showed a higher similarity to eukaryotic PetCs than to other prokaryotic PetCs. The structure also revealed a deep pocket on the PetC surface which is oriented towards the membrane surface in the whole complex. Its surface properties suggest a binding site for a hydrophobic compound and the complete conservation of the pocket-forming residues in all known PetC sequences indicates the functional importance of this pocket in the cytochrome b(6)f complex.

Rieske Iron-Sulfur Protein Movement and Conformational Changes in Cytochrome bc–bf Complexes

“…The soluble Rieske fragment from a cyanobacterium, Thermosynechococcus elongatus (3AZC, 2.0 Å), also has a cis peptide here (Veit et al 2012), while that from T. thermophilus (1NYK, 1.3 Å) has a trans peptide in this place (Hunsicker-Wang et al 2003) Structures of the entire b 6 f complex are evenly divided as to whether this should be a cis peptide in the b 6 f protein. However, given the lower resolution of these structures and the relatively high B factors of the ISP-ED in the complex due to its mobility, this should probably not be taken as evidence of cis -trans conformational switching in the protein.…”

Transmembrane signaling and assembly of the cytochrome b6f-lipidic charge transfer complex

“…Structures of the ~250 residue cyt f peripheral domain have been obtained from C. reinhardtii [14, 15], Phormidium laminosum [16], Brassica rapa [17-19], while those of the ISP soluble domain have been solved from tryptic fragments of the ISP protein isolated from Thermosynechococcus elongates [20] and Spinacia olearcea [21]. While the trans-membrane region of the b 6 f complex consists of α -helices, the N-terminal soluble domain of cyt f has an elongate β — sheet structure ( Fig.…”

Functional Characterization of the Small Regulatory Subunit PetP from the Cytochrome b6f Complex in Thermosynechococcus elongatus

“…The four large subunits cytochrome f (cyt f), cytochrome b 6 (cyt b 6 ), the Rieske iron-sulfur protein, and subunit IV (SU IV) are directly involved in electron transport, while the four small subunits PetG, PetL, PetM, and PetN are apparently involved in the structural stabilization of the complex. The more highly resolved crystal structures of the lumen-exposed water soluble parts of the complex, i.e., cyt f and the Rieske protein, suggest novel structural features for proton transport (Carrell et al, 1999) and regulation of the Rieske domain movement (Carrell et al, 1999;Bernat and Rögner, 2011;Kallas, 2012;Veit et al, 2012). (A) Elution profile from a preparative IMAC column (first purification step): peak 1 with nonspecifically bound proteins, mainly NADH-dehydrogenase and PSI, peak 2 with enriched b 6 f. Chelating sepharose Fast Flow (GE Healthcare), 0.5 mL/min, 4°C, gradient: 10 to 100 mM histidine.…”