QCR6/YFR033C Summary Help

Standard Name QCR6 1
Systematic Name YFR033C
Alias COR3 1 , UCR6
Feature Type ORF, Verified
Description Subunit 6 of the ubiquinol cytochrome-c reductase complex; the complex, also known as the cytochrome bc(1) complex or Complex III, is a component of the mitochondrial inner membrane electron transport chain; highly acidic protein; required for maturation of cytochrome c1; may be loosely associated with the complex since it is easily released into the intermembrane space (2, 3, 4 and see Summary Paragraph)
Name Description ubiQuinol-cytochrome C oxidoReductase 1
Chromosomal Location
ChrVI:224769 to 224326 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All QCR6 GO evidence and references
  View Computational GO annotations for QCR6
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 9 genes
Classical genetics
Large-scale survey
86 total interaction(s) for 68 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 3
  • Affinity Capture-RNA: 3
  • Affinity Capture-Western: 5
  • Biochemical Activity: 3
  • Protein-RNA: 1
  • Two-hybrid: 1

Genetic Interactions
  • Negative Genetic: 61
  • Positive Genetic: 2
  • Synthetic Growth Defect: 4
  • Synthetic Haploinsufficiency: 1
  • Synthetic Lethality: 1
  • Synthetic Rescue: 1

Expression Summary
Length (a.a.) 147
Molecular Weight (Da) 17,257
Isoelectric Point (pI) 3.81
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrVI:224769 to 224326 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..444 224769..224326 2011-02-03 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000001929

The cytochrome bc1 complex (also known as ubiquinol:cytochrome c oxidoreductase, ubiquinol:ferricytochrome c oxidoreductase, and respiratory complex III) is a highly conserved enzyme of the mitochondrial respiratory chain (reviewed in 5). In S. cerevisiae it consists of three catalytic subunits, Cobp, Rip1p, and Cyt1p, plus seven additional subunits: Cor1p, Qcr2p, Qcr6p, Qcr7p, Qcr8p, Qcr9p, and Qcr10p (5, 6). The crystal structure of the complex shows that two functional units, each containing these ten subunits, associate with each other in the mitochondrial inner membrane (7). Assembly of a functional complex requires two proteins, Cbp3p and Cbp4p, that are not components of the complex but may associate with it during assembly (8). It also requires Bcs1p, an AAA-family ATPase that interacts with a precursor of the complex to mediate incorporation of the Rip1p and Qcr10p subunits (9). The mechanism of energy transfer by the complex, known as the protonmotive Q cycle, has been studied in detail (reviewed in 5). The net result of the Q cycle is the stepwise transfer of an electron through the complex from ubiquinol to cytochrome c (Cyc1p), coupled with the translocation of a proton across the mitochondrial inner membrane (5). The function of the cytochrome bc1 complex is essential to the energy-generating process of oxidative phosphorylation, which is carried out by the enzyme complexes of the mitochondrial respiratory chain.

Qcr6p is required for activity of the cytochrome bc1 complex at high temperature: the null mutant displays normal respiratory growth at 30 degrees C, but is unable to respire and lacks complex III activity at 37 degrees (2). At the nonpermissive temperature, the qcr6 null mutant also accumulates unprocessed cytochrome c1 (Cyt1p) (2). The response to varying ionic strength of complex III activity in the qcr6 null mutant suggests that the relatively acidic Qcr6p may have a role in association of the basic cytochrome c (Cyc1p) with the complex (10). Qcr6p has a 25-amino acid presequence that is cleaved upon mitochondrial import but, in contrast to most other mitochondrial presequences, is not required for import (11). Qcr6p is conserved in other eukaryotes and is homologous to the so-called "hinge" protein subunit of bovine complex III, which is thought to mediate interaction between cytochromes c1 and c (3).

Last updated: 2007-07-26 Contact SGD

References cited on this page View Complete Literature Guide for QCR6
1) Schmitt ME and Trumpower BL  (1990) Subunit 6 regulates half-of-the-sites reactivity of the dimeric cytochrome bc1 complex in Saccharomyces cerevisiae. J Biol Chem 265(28):17005-11
2) Yang M and Trumpower BL  (1994) Deletion of QCR6, the gene encoding subunit six of the mitochondrial cytochrome bc1 complex, blocks maturation of cytochrome c1, and causes temperature-sensitive petite growth in Saccharomyces cerevisiae. J Biol Chem 269(2):1270-5
3) van Loon AP, et al.  (1984) The DNA sequence of the nuclear gene coding for the 17-kd subunit VI of the yeast ubiquinol-cytochrome c reductase: a protein with an extremely high content of acidic amino acids. EMBO J 3(5):1039-43
4) Voegtle FN, et al.  (2012) Intermembrane space proteome of yeast mitochondria. Mol Cell Proteomics 11(12):1840-52
5) Hunte C, et al.  (2003) Protonmotive pathways and mechanisms in the cytochrome bc1 complex. FEBS Lett 545(1):39-46
6) Brandt U, et al.  (1994) Isolation and characterization of QCR10, the nuclear gene encoding the 8.5-kDa subunit 10 of the Saccharomyces cerevisiae cytochrome bc1 complex. J Biol Chem 269(17):12947-53
7) Hunte C, et al.  (2000) Structure at 2.3 A resolution of the cytochrome bc(1) complex from the yeast Saccharomyces cerevisiae co-crystallized with an antibody Fv fragment. Structure 8(6):669-84
8) Kronekova Z and Rodel G  (2005) Organization of assembly factors Cbp3p and Cbp4p and their effect on bc(1) complex assembly in Saccharomyces cerevisiae. Curr Genet 47(4):203-12
9) Cruciat CM, et al.  (1999) Bcs1p, an AAA-family member, is a chaperone for the assembly of the cytochrome bc(1) complex. EMBO J 18(19):5226-33
10) Schoppink PJ, et al.  (1989) The effect of deletion of the genes encoding the 40 kDa subunit II or the 17 kDa subunit VI on the steady-state kinetics of yeast ubiquinol-cytochrome-c oxidoreductase. Biochim Biophys Acta 974(2):192-201
11) DeLabre ML, et al.  (1999) The cleaved presequence is not required for import of subunit 6 of the cytochrome bc1 complex into yeast mitochondria or assembly into the complex. FEBS Lett 449(2-3):201-5