QCR9/YGR183C Summary Help

Standard Name QCR9 1
Systematic Name YGR183C
Alias UCR9
Feature Type ORF, Verified
Description Subunit 9 of ubiquinol cytochrome-c reductase (Complex III); Complex III is a component of the mitochondrial inner membrane electron transport chain; required for electron transfer at the ubiquinol oxidase site of the complex (1, 2 and see Summary Paragraph)
Name Description ubiQuinol-cytochrome C oxidoReductase 1
Chromosomal Location
ChrVII:859476 to 859063 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Genetic position: 148 cM
Gene Ontology Annotations All QCR9 GO evidence and references
  View Computational GO annotations for QCR9
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 4 genes
Classical genetics
Large-scale survey
154 total interaction(s) for 119 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 3
  • Affinity Capture-Western: 1
  • PCA: 3
  • Protein-RNA: 1

Genetic Interactions
  • Negative Genetic: 125
  • Positive Genetic: 14
  • Synthetic Growth Defect: 4
  • Synthetic Rescue: 3

Expression Summary
Length (a.a.) 66
Molecular Weight (Da) 7,476
Isoelectric Point (pI) 5.77
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrVII:859476 to 859063 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Genetic position: 148 cM
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..3 859476..859474 2011-02-03 1996-07-31
Intron 4..216 859473..859261 2011-02-03 1996-07-31
CDS 217..414 859260..859063 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 SGDIDS000003415

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 3). 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 (3, 4). 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 (5). 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 (6). 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 (7). The mechanism of energy transfer by the complex, known as the protonmotive Q cycle, has been studied in detail (reviewed in 3). 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 (3). 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.

Qcr9p, the smallest subunit of the cytochrome bc1 complex (7.3 kDa), is essential for the correct structure and function of the complex as well as for respiratory growth (1). In the qcr9 null mutant, the cytochrome bc1 complex lacks electron transfer at the ubiquinol oxidase site (known as center P) (2) because it is improperly assembled, such that the iron-sulfur cluster-containing subunit Rip1p is unstable and has reduced function (8). QCR9 is conserved across eukaryotes (9, 10, 1).

Last updated: 2007-07-26 Contact SGD

References cited on this page View Complete Literature Guide for QCR9
1) Phillips JD, et al.  (1990) Isolation and characterization of QCR9, a nuclear gene encoding the 7.3-kDa subunit 9 of the Saccharomyces cerevisiae ubiquinol-cytochrome c oxidoreductase complex. An intron-containing gene with a conserved sequence occurring in the intron of COX4. J Biol Chem 265(34):20813-21
2) Graham LA, et al.  (1992) Deletion of subunit 9 of the Saccharomyces cerevisiae cytochrome bc1 complex specifically impairs electron transfer at the ubiquinol oxidase site (center P) in the bc1 complex. FEBS Lett 313(3):251-4
3) Hunte C, et al.  (2003) Protonmotive pathways and mechanisms in the cytochrome bc1 complex. FEBS Lett 545(1):39-46
4) 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
5) 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
6) 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
7) 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
8) Phillips JD, et al.  (1993) Subunit 9 of the Saccharomyces cerevisiae cytochrome bc1 complex is required for insertion of EPR-detectable iron-sulfur cluster into the Rieske iron-sulfur protein. J Biol Chem 268(16):11727-36
9) Braun HP  (1996) Identification of novel homologues of three low molecular weight subunits of the mitochondrial bc1 complex. Mol Biol Rep 23(2):71-7
10) Frolov MV, et al.  (2000) The oxen gene of Drosophila encodes a homolog of subunit 9 of yeast ubiquinol-cytochrome c oxidoreductase complex: evidence for modulation of gene expression in response to mitochondrial activity. Genetics 156(4):1727-36