UQCRQ explained

Ubiquinol-cytochrome c reductase, complex III subunit VII, 9.5kDa is a protein that in humans is encoded by the UQCRQ gene. This ubiqinone-binding protein is a subunit of mitochondrial Complex III in the electron transport chain. A mutation in the UQCRQ gene has been shown to cause severe neurological disorders.^[1] Infection by Trypanosoma cruzi can cause oxidative modification of this protein in cardiac muscle tissue.^[2]

Structure

The UQCRQ gene is located on the q arm of chromosome 5 in position 31.1 and spans 2,217 base pairs.^[3] The gene produces a 9.9 kDa protein composed of 82 amino acids.^{[4] [5]} This protein is transmembranous, with more mass on the matrix side of the membrane.^[6]

Function

This gene encodes a ubiquinone-binding protein of low molecular mass. It is a small core-associated protein and a subunit of ubiquinol-cytochrome c reductase complex III, which is part of the mitochondrial respiratory chain.^[7]

Clinical significance

Variants of UQCRQ have been associated with complex III deficiency. One set of twenty consanguineous cases of a Ser45Phe mutation in the UQCRQ gene, and a different homozygous 4-bp deletion at p. 338-341, have been linked to this disease. In an inbred Israeli Bedouin family, the mutations, inherited in an autosomal recessive pattern, displayed the phenotype of mitochondrial Complex III deficiency, nuclear type 4, accompanied by severe neurological symptoms. Other symptoms of complex III deficiency linked to these mutations have included hypoglycemia, lactic acidosis, and hypotonia.^[8]

In another study of cardiac muscle tissue in individuals infected by Trypanosoma cruzi, an oxidative modification of the UQCRQ subunit was present, along with oxidative modification of subunits UQCRC1 and UQCRC2 of the same core complex and UQCRH and CYC1 of the neighboring subcomplex.

Interactions

The protein encoded by UQCRQ has protein-protein interactions with UQCRC1, OPTN, ERCC8, GRINL1A, Dctn1, K8.1, XRCC3, PML, RAB7A, HNRNPA1L2, CDC73, NLRP3, HAUS2, TMEM248, and GOLT1B.^[9]

Further reading

• Book: Schägger H, Brandt U, Gencic S, von Jagow G . Ubiquinol-cytochrome-c reductase from human and bovine mitochondria . [7] Ubiquinol-cytochrome-c reductase from human and bovine mitochondria . Methods in Enzymology . 260 . 82–96 . 1995 . 8592474 . 10.1016/0076-6879(95)60132-5 . 9780121821616 .
• Sifroni KG, Damiani CR, Stoffel C, Cardoso MR, Ferreira GK, Jeremias IC, Rezin GT, Scaini G, Schuck PF, Dal-Pizzol F, Streck EL . Mitochondrial respiratory chain in the colonic mucosal of patients with ulcerative colitis . Molecular and Cellular Biochemistry . 342 . 1–2 . 111–5 . September 2010 . 20440543 . 10.1007/s11010-010-0474-x . 34103232 .

Notes and References

1. Barel O, Shorer Z, Flusser H, Ofir R, Narkis G, Finer G, Shalev H, Nasasra A, Saada A, Birk OS . Mitochondrial complex III deficiency associated with a homozygous mutation in UQCRQ . American Journal of Human Genetics . 82 . 5 . 1211–6 . May 2008 . 18439546 . 2427202 . 10.1016/j.ajhg.2008.03.020 .
2. Wen JJ, Garg N . Oxidative modification of mitochondrial respiratory complexes in response to the stress of Trypanosoma cruzi infection . Free Radical Biology & Medicine . 37 . 12 . 2072–81 . December 2004 . 15544925 . 10.1016/j.freeradbiomed.2004.09.011 .
3. Web site: Entrez Gene: Ubiquinol-cytochrome c reductase, complex III subunit VII, 9.5kDa.
4. Zong NC, Li H, Li H, Lam MP, Jimenez RC, Kim CS, Deng N, Kim AK, Choi JH, Zelaya I, Liem D, Meyer D, Odeberg J, Fang C, Lu HJ, Xu T, Weiss J, Duan H, Uhlen M, Yates JR, Apweiler R, Ge J, Hermjakob H, Ping P . Integration of cardiac proteome biology and medicine by a specialized knowledgebase . Circulation Research . 113 . 9 . 1043–53 . October 2013 . 23965338 . 4076475 . 10.1161/CIRCRESAHA.113.301151 .
5. Web site: UQCRQ - Cytochrome b-c1 complex subunit 8 . Cardiac Organellar Protein Atlas Knowledgebase (COPaKB) .
6. Usui S, Yu L, Yu CA . The small molecular mass ubiquinone-binding protein (QPc-9.5 kDa) in mitochondrial ubiquinol-cytochrome c reductase: isolation, ubiquinone-binding domain, and immunoinhibition . Biochemistry . 29 . 19 . 4618–26 . May 1990 . 2164842 . 10.1021/bi00471a017 .
7. Web site: Entrez Gene: Ubiquinol-cytochrome c reductase, complex III subunit VII, 9.5kDa.
8. Haut S, Brivet M, Touati G, Rustin P, Lebon S, Garcia-Cazorla A, Saudubray JM, Boutron A, Legrand A, Slama A . A deletion in the human QP-C gene causes a complex III deficiency resulting in hypoglycaemia and lactic acidosis . Human Genetics . 113 . 2 . 118–22 . July 2003 . 12709789 . 10.1007/s00439-003-0946-0 . 24273072 .
9. Web site: Interactions with UQCRQ. IntAct. www.ebi.ac.uk. en. 2018-08-02.