Protein Family Models

This is the N-terminal region of the E or R chain, Ubiquitinol-cytochrome C reductase Fe-S subunit, of the hetero-hexameric cytochrome bc1 complex. This region is a TAT-signal region. The cytochrome bc1 complex is an oligomeric membrane protein complex that is a component of respiratory and photosynthetic electron transfer chains. The enzyme couples the transfer of electrons from ubiquinol to cytochrome c with the the generation of a protein gradient across the membrane [1]. The motif is also associated with Rieske (Pfam:PF00355), UCR_TM (Pfam:PF02921) and Ubiq-Cytc-red_N (Pfam:PF09165). [1]. 10873857. Structure at 2.3 A resolution of the cytochrome bc(1) complex from the yeast Saccharomyces cerevisiae co-crystallized with an antibody Fv fragment. Hunte C, Koepke J, Lange C, Rossmanith T, Michel H;. Structure. 2000;8:669-684. (from Pfam)

Date:

2024-10-16

The rieske domain has a [2Fe-2S] centre. Two conserved cysteines coordinate one Fe ion, while the other Fe ion is coordinated by two conserved histidines. In hyperthermophilic archaea there is a SKTPCX(2-3)C motif at the C-terminus. The cysteines in this motif form a disulphide bridge, which stabilises the protein [4]. [1]. 8736555. 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 A resolution. Iwata S, Saynovits M, Link TA, Michel H. Structure 1996;4:567-579. [2]. 1961737. Functional analysis in yeast of cDNA coding for the mitochondrial Rieske iron-sulfur protein of higher plants. Huang JT, Struck F, Matzinger DF, Levings CS;. Proc Natl Acad Sci U S A 1991;88:10716-10720. [3]. 8386158. The mitochondrial targeting presequence of the Rieske iron-sulfur protein is processed in a single step after insertion into the cytochrome bc1 complex in mammals and retained as a subunit in the complex. Brandt U, Yu L, Yu CA, Trumpower BL;. J Biol Chem 1993;268:8387-8390. [4]. 19862563. Role of a novel disulfide bridge within the all-beta fold of soluble Rieske proteins. Botelho HM, Leal SS, Veith A, Prosinecki V, Bauer C, Frohlich R, Kletzin A, Gomes CM;. J Biol Inorg Chem. 2010;15:271-281. (from Pfam)

Date:

2024-10-16

This model represents the Proteobacterial and mitochondrial type of the Rieske [2Fe-2S] iron-sulfur as found in ubiquinol-cytochrome c reductase. The model excludes the Rieske iron-sulfur protein as found in the cytochrome b6-f complex of the Cyanobacteria and chloroplasts. Most members of this family have a recognizable twin-arginine translocation (tat) signal sequence (DeltaPh-dependent translocation in chloroplast) for transport across the membrane with the 2Fe-2S group already bound. These signal sequences include a motif resembling RRxFLK before the transmembrane helix.

Gene:

petA

Date:

2021-04-27

Many proteins that fold in the cytosol because a required cofactor is available there only, or because cytosolic chaperones assist in folding, or because high salt in the extracellular milieu would interfere with folding there, cannot rely on the standard general secretory (Sec) pathway for secretion across the plasma membrane. This model describes a family of predicted long, non-Sec signal sequences and signal-anchor sequences (uncleaved signal sequences). All contain a typically invariant pair of arginine residues, in a motif approximated by (S/T)-R-R-X-F-L-K, followed by a membrane-spanning hydrophobic region. The system that secretes pre-folded proteins with this motif is known as twin-arginine translocation, or TAT. Note that some variant forms, often lineage-specific ones such as the RKxFL version found in Leptospira, do occur but typically fall outside the scope of this HMM. Twin-arginine signal domains with small amino acid side chains at the -1 and -3 positions from the C-terminus of the model should be predicted to be cleaved as are Sec pathway signal sequences. The system, although far from universal in prokaryotes, is widespread in bacteria and present also in many archaea.

Date:

2019-11-27

ubiquinol-cytochrome c reductase iron-sulfur subunit is a component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is a respiratory chain that generates an electrochemical potential coupled to ATP synthesis

Date:

2018-03-09