TMEM126B explained

Transmembrane protein 126B is a protein that in humans is encoded by the TMEM126B gene.[1] [2] TMEM126B is a mitochondrial transmembrane protein which is a component of the mitochondrial complex I assembly complex. The TMEM126B gene is conserved in mammals.[3] The encoded protein serves as an assembly factor that is required for formation of the membrane arm of the complex. It interacts with NADH dehydrogenase [ubiquinone] 1 alpha subcomplex assembly factor 13. Naturally occurring mutations in this gene are associated with isolated complex I deficiency. A pseudogene of this gene has been defined on chromosome 9.

Structure

TMEM126B is located on the q arm of chromosome 11 in position 14.1 and has 7 exons. The TMEM126B gene produces a 4.6 kDa protein composed of 54 amino acids.[4] [5] It is a part of the mitochondrial complex I assembly (MCIA) complex, composed of NDUFAF1, ECSIT, and ACAD9 (by similarity). It associates with the intermediate 370 kDa subcomplex of incompletely assembled complex I.[6] Complex I is composed of 45 evolutionally conserved core subunits, including both mitochondrial DNA and nuclear encoded subunits. One of its arms is embedded in the inner membrane of the mitochondria, and the other is embedded in the organelle. The two arms are arranged in an L-shaped configuration. The total molecular weight of the complex is 1MDa.[7] A cartoon representation of the predicted orientation of TMEM126B within cell membrane, tentatively based on the phosphorylation and hydrophobicity data is shown below.

Function

The TMEM126B gene encodes a mitochondrial transmembrane protein which is a component of the mitochondrial complex I assembly complex. The encoded protein serves as an assembly factor that is required for formation of the membrane arm of the complex. TMEM126B comigrates with other assembly factors including ACAD9, CIA30, and ECSIT. In the absence of TMEM126B, such assembly factors were not recruited into the mitochondrial membrane, and did not participate in complex I assembly. Dysfunction of TMEM126B has known to cause several complications in complex I characterized by severe difficulties in mitochondrial respiration and the complete failure of complex I assembly. However, it is not known to have significant effect on the assemblies of mitochondrial complexes III, IV, and V.[8]

Clinical Significance

Mutations in TMEM126B is known to result in mitochondrial diseases and associated disorders. It is majorly associated with a complex I deficiency, a deficiency in the first complex of the mitochondrial respiratory chain. A complex I deficiency involving the dysfunction of the mitochondrial respiratory chain may cause a wide range of clinical manifestations from lethal neonatal disease to adult-onset neurodegenerative disorders. Phenotypes include macrocephaly with progressive leukodystrophy, non-specific encephalopathy, cardiomyopathy, Leigh syndrome, myopathy, liver disease, Leber hereditary optic neuropathy, and some forms of Parkinson disease. In addition to complex I deficiency, TMEM126B mutations also show association with severe multi-system disorders during infancy, such as chronic renal failure and cardiomyopathy, and myopathy in childhood or adulthood.

Discovery

TMEM126B was first discovered in a study of protein expression in tissues of the hypothalamus-pituitary-adrenal axis using full cDNA cloning.[2] It has since been detected in other tissues.[9]

Gene

TMEM126B is located on chromosome 11 in humans, flanked by the following genes:[10]

Translation

A conceptual translation of the TMEM126B protein, including a projection of the secondary structure,[13] predictions of transmembrane regions,[14] and putative phosphorylation[15] and glycation sites[16] is included below:

Tissue distribution

TMEM126B is expressed in most tissue types, with the notable exceptions of adipose tissue, ear tissue, the larynx, lymph tissue, nerve tissue, pituitary gland, spleen, thymus, thyroid, trachea, and umbilical cord.[17] It also appears to be highly expressed in parathyroid, bone marrow, and urinary bladder tissue.[17] There is also evidence that one of the isoforms of TMEM126B is expressed in the cell membrane of memory B cells of the adaptive immune system.[18]

Predicted properties

The following properties of TMEM126B were predicted using bioinformatic analysis:

Interactions

In addition to co-subunits for complex I, TMEM126B has protein-protein interactions with ECSIT, NDUFAF1, NDUFC2, NDUFA13, and others.

Further reading

Notes and References

  1. Web site: Entrez Gene: transmembrane protein 126B.
  2. Hu RM, Han ZG, Song HD, Peng YD, Huang QH, Ren SX, Gu YJ, Huang CH, Li YB, Jiang CL, Fu G, Zhang QH, Gu BW, Dai M, Mao YF, Gao GF, Rong R, Ye M, Zhou J, Xu SH, Gu J, Shi JX, Jin WR, Zhang CK, Wu TM, Huang GY, Chen Z, Chen MD, Chen JL . 6 . Gene expression profiling in the human hypothalamus-pituitary-adrenal axis and full-length cDNA cloning . Proceedings of the National Academy of Sciences of the United States of America . 97 . 17 . 9543–8 . August 2000 . 10931946 . 16901 . 10.1073/pnas.160270997 . 2000PNAS...97.9543H . free .
  3. Web site: HomoloGene Results: TMEM126B transmembrane protein 126B.
  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 . 6 . 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: Cardiac Organellar Protein Atlas Knowledgebase (COPaKB) —— Protein Information. Yao. Daniel. amino.heartproteome.org. 2018-07-27.
  6. Web site: Complex I assembly factor TMEM126B, mitochondrial. www.uniprot.org. en. 2018-07-27.
  7. Rhein VF, Carroll J, Ding S, Fearnley IM, Walker JE . NDUFAF5 Hydroxylates NDUFS7 at an Early Stage in the Assembly of Human Complex I . The Journal of Biological Chemistry . 291 . 28 . 14851–60 . July 2016 . 27226634 . 4938201 . 10.1074/jbc.M116.734970 . free .
  8. Alston CL, Compton AG, Formosa LE, Strecker V, Oláhová M, Haack TB, Smet J, Stouffs K, Diakumis P, Ciara E, Cassiman D, Romain N, Yarham JW, He L, De Paepe B, Vanlander AV, Seneca S, Feichtinger RG, Płoski R, Rokicki D, Pronicka E, Haller RG, Van Hove JL, Bahlo M, Mayr JA, Van Coster R, Prokisch H, Wittig I, Ryan MT, Thorburn DR, Taylor RW . 6 . Biallelic Mutations in TMEM126B Cause Severe Complex I Deficiency with a Variable Clinical Phenotype . American Journal of Human Genetics . 99 . 1 . 217–27 . July 2016 . 27374774 . 5005451 . 10.1016/j.ajhg.2016.05.021 .
  9. Strausberg RL, Feingold EA, Grouse LH, Derge JG, Klausner RD, Collins FS, Wagner L, Shenmen CM, Schuler GD, Altschul SF, Zeeberg B, Buetow KH, Schaefer CF, Bhat NK, Hopkins RF, Jordan H, Moore T, Max SI, Wang J, Hsieh F, Diatchenko L, Marusina K, Farmer AA, Rubin GM, Hong L, Stapleton M, Soares MB, Bonaldo MF, Casavant TL, Scheetz TE, Brownstein MJ, Usdin TB, Toshiyuki S, Carninci P, Prange C, Raha SS, Loquellano NA, Peters GJ, Abramson RD, Mullahy SJ, Bosak SA, McEwan PJ, McKernan KJ, Malek JA, Gunaratne PH, Richards S, Worley KC, Hale S, Garcia AM, Gay LJ, Hulyk SW, Villalon DK, Muzny DM, Sodergren EJ, Lu X, Gibbs RA, Fahey J, Helton E, Ketteman M, Madan A, Rodrigues S, Sanchez A, Whiting M, Madan A, Young AC, Shevchenko Y, Bouffard GG, Blakesley RW, Touchman JW, Green ED, Dickson MC, Rodriguez AC, Grimwood J, Schmutz J, Myers RM, Butterfield YS, Krzywinski MI, Skalska U, Smailus DE, Schnerch A, Schein JE, Jones SJ, Marra MA . 6 . Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences . Proceedings of the National Academy of Sciences of the United States of America . 99 . 26 . 16899–903 . December 2002 . 12477932 . 139241 . 10.1073/pnas.242603899 . 2002PNAS...9916899M . free .
  10. Web site: https://www.ncbi.nlm.nih.gov/mapview/maps.cgi?TAXID=9606&CHR=11&MAPS=model,ugHs,ensgenes,rna,genes[85323889.04%3A85363310.96-r&QSTR=55863[gene_id]&QUERY=uid%2816330121%29&ZOOM=0.0584 TMEM126B in Map Viewer].
  11. Web site: Entrez Gene: TMEM126A transmembrane protein 126A.
  12. Web site: OMIM Zhangfei protein.
  13. Burgess AW, Ponnuswamy PK, Sheraga HA . Analysis of conformations of amino acid residues and prediction of backbone topography in proteins. . Israel Journal of Chemistry . 12 . 1–2. 239–286 . 1974 . 10.1002/ijch.197400022.
  14. Persson B, Argos P . Prediction of transmembrane segments in proteins utilising multiple sequence alignments . Journal of Molecular Biology . 237 . 2 . 182–92 . March 1994 . 8126732 . 10.1006/jmbi.1994.1220 .
  15. Web site: NetPhos 2.0 predictions for TMEM126B.
  16. Web site: NetGlycate 1.0 predictions for TMEM126B.
  17. Web site: EST profile - Hs.525063.
  18. Web site: CELLS BELONGING TO THE ADAPTIVE IMMUNE SYSTEM THAT EXPRESS PAQ ISOFORM OF TMEM126B .
  19. Brendel V, Bucher P, Nourbakhsh IR, Blaisdell BE, Karlin S . Methods and algorithms for statistical analysis of protein sequences . Proceedings of the National Academy of Sciences of the United States of America . 89 . 6 . 2002–6 . March 1992 . 1549558 . 48584 . 10.1073/pnas.89.6.2002 . 1992PNAS...89.2002B . free .
  20. Web site: PI Program (Isoelectric Point Prediction) . dead . https://web.archive.org/web/20081026062821/http://www.embl-heidelberg.de/cgi/pi-wrapper.pl . 2008-10-26 .
  21. Bendtsen JD, Nielsen H, von Heijne G, Brunak S . Improved prediction of signal peptides: SignalP 3.0 . Journal of Molecular Biology . 340 . 4 . 783–95 . July 2004 . 15223320 . 10.1016/j.jmb.2004.05.028 . 10.1.1.165.2784 .

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