QCR2/YPR191W Summary Help

Standard Name QCR2 1
Systematic Name YPR191W
Alias COR2 2 , UCR2 3
Feature Type ORF, Verified
Description Subunit 2 of ubiquinol cytochrome-c reductase (Complex III); Complex III is a component of the mitochondrial inner membrane electron transport chain; phosphorylated; transcription is regulated by Hap1p, Hap2p/Hap3p, and heme (2, 4, 5 and see Summary Paragraph)
Name Description QH2:cytochrome-C oxidoReductase 4
Chromosomal Location
ChrXVI:919381 to 920487 | ORF Map | GBrowse
Gene Ontology Annotations All QCR2 GO evidence and references
  View Computational GO annotations for QCR2
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 1 genes
Classical genetics
Large-scale survey
196 total interaction(s) for 172 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 35
  • Affinity Capture-RNA: 1
  • Affinity Capture-Western: 15
  • Two-hybrid: 4

Genetic Interactions
  • Dosage Lethality: 1
  • Negative Genetic: 125
  • Positive Genetic: 13
  • Synthetic Growth Defect: 1
  • Synthetic Rescue: 1

Expression Summary
Length (a.a.) 368
Molecular Weight (Da) 40,478
Isoelectric Point (pI) 8.34
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXVI:919381 to 920487 | ORF Map | GBrowse
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1107 919381..920487 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 SGDIDS000006395

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 6). 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 (6, 7). 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 (8). 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 (9). 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 (10). The mechanism of energy transfer by the complex, known as the protonmotive Q cycle, has been studied in detail (reviewed in 6). 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 (6). 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.

Qcr2p, Cor1p, and Qcr7p comprise a large domain of the cytochrome bc1 complex that extends into the mitochondrial matrix (6). Qcr2p, one of the so-called "core" subunits, is very important for activity of the cytochrome bc1 complex; the null mutation has been described as causing either a severe decrease or a total block in complex III activity and respiratory growth (4, 11). These defects can be suppressed by a point mutation in the mitochondrial cob gene encoding cytochrome b (12). QCR2 is conserved across eukaryotes (13) and is homologous to human UQCRC2 (14; OMIM).

Last updated: 2007-07-26 Contact SGD

References cited on this page View Complete Literature Guide for QCR2
1) Einerhand AW, et al.  (1995) The upstream region of the FOX3 gene encoding peroxisomal 3-oxoacyl-coenzyme A thiolase in Saccharomyces cerevisiae contains ABF1- and replication protein A-binding sites that participate in its regulation by glucose repression. Mol Cell Biol 15(6):3405-14
2) Dorsman JC and Grivell LA  (1990) Expression of the gene encoding subunit II of yeast QH2: cytochrome c oxidoreductase is regulated by multiple factors. Curr Genet 17(6):459-64
3) Chiannilkulchai N, et al.  (1992) RPC82 encodes the highly conserved, third-largest subunit of RNA polymerase C (III) from Saccharomyces cerevisiae. Mol Cell Biol 12(10):4433-40
4) Oudshoorn P, et al.  (1987) Subunit II of yeast QH2:cytochrome-c oxidoreductase. Nucleotide sequence of the gene and features of the protein. Eur J Biochem 163(1):97-103
5) Reinders J, et al.  (2007) Profiling phosphoproteins of yeast mitochondria reveals a role of phosphorylation in assembly of the ATP synthase. Mol Cell Proteomics 6(11):1896-906
6) Hunte C, et al.  (2003) Protonmotive pathways and mechanisms in the cytochrome bc1 complex. FEBS Lett 545(1):39-46
7) 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
8) 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
9) 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
10) 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
11) Crivellone MD, et al.  (1988) Assembly of the mitochondrial membrane system. Analysis of structural mutants of the yeast coenzyme QH2-cytochrome c reductase complex. J Biol Chem 263(28):14323-33
12) di Rago JP, et al.  (1997) A point mutation in the mitochondrial cytochrome b gene obviates the requirement for the nuclear encoded core protein 2 subunit in the cytochrome bc1 complex in Saccharomyces cerevisiae. J Biol Chem 272(8):4699-704
13) Trumpower BL  (1990) Cytochrome bc1 complexes of microorganisms. Microbiol Rev 54(2):101-29
14) Hosokawa Y, et al.  (1989) Complementary DNA encoding core protein II of human mitochondrial cytochrome bc1 complex. Substantial diversity in deduced primary structure from its yeast counterpart. J Biol Chem 264(23):13483-8