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Protein P4HB PDB 1bjx.png
Available structures
PDBOrtholog search: PDBe RCSB
AliasesP4HB, DSI, ERBA2L, GIT, P4Hbeta, PDI, PDIA1, PHDB, PO4DB, PO4HB, PROHB, CLCRP1, prolyl 4-hydroxylase subunit beta
External IDsMGI: 97464 HomoloGene: 55495 GeneCards: P4HB
Gene location (Human)
Chromosome 17 (human)
Chr.Chromosome 17 (human)[1]
Chromosome 17 (human)
Genomic location for P4HB
Genomic location for P4HB
Band17q25.3Start81,843,159 bp[1]
End81,860,694 bp[1]
RNA expression pattern
PBB GE P4HB 200656 s at fs.png

PBB GE P4HB 200654 at fs.png
More reference expression data
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 17: 81.84 – 81.86 MbChr 11: 120.56 – 120.57 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

Protein disulfide-isomerase, also known as the beta-subunit of prolyl 4-hydroxylase (P4HB), is an enzyme that in humans encoded by the P4HB gene. The human P4HB gene is localized in chromosome 17q25.[5][6][7][8] Unlike other prolyl 4-hydroxylase family proteins, this protein is multifunctional and acts as an oxidoreductase for disulfide formation, breakage, and isomerization.[9] The activity of P4HB is tightly regulated. Both dimer dissociation and substrate binding are likely to enhance its enzymatic activity during the catalysis process.[10][11]


P4HB has four thioredoxin domains (a, b, b’, and a’), with two CGHC active sites in the a and a’ domains. In both the reduced and oxidized state, these domains are arranged as a horseshoe shape. In reduced P4HB, domains a, b, and b' are in the same plane, while domain a' twists out at an ∼45° angle. When oxidized, the four domains stay in the same plane, and the distance between the active sites is larger than that in the reduced state. The oxidized form also exposes more hydrophobic areas and possesses a larger cleft to facilitate substrate binding.[12][13] P4HB has been shown to dimerize in vivo via noncatalytic bb' domains. Formation of dimer blocks substrate-binding site and inhibits P4HB’s activity.[14]


This gene encodes the beta subunit of prolyl 4-hydroxylase, a highly abundant multifunctional enzyme that belongs to the protein disulfide isomerase family. When present as a tetramer consisting of two alpha and two beta subunits, this enzyme is involved in hydroxylation of prolyl residues in preprocollagen. This enzyme is also a disulfide isomerase containing two thioredoxin domains that catalyze the formation, breakage and rearrangement of disulfide bonds. Other known functions include its ability to act as a chaperone that inhibits aggregation of misfolded proteins in a concentration-dependent manner, its ability to bind thyroid hormone, its role in both the influx and efflux of S-nitrosothiol-bound nitric oxide, and its function as a subunit of the microsomal triglyceride transfer protein complex.[6]

Clinical significance[edit]

P4HB is a risk factor of amyotrophic lateral sclerosis (ALS). Studies have shown significant genotypic associations for two SNPs in P4HB with FALS (familial ALS), rs876016 (P=0.0198) and rs2070872 (P=0.0046). Together with other ER stress markers, P4HB is greatly elevated in ALS spinal cord.[15] P4HB can also be nitrosylated, and elevation of nitrosylated P4HB has been shown in Parkinson's and Alzheimer's disease brain tissue, as well as in transgenic mutant superoxide dismutase 1 mouse and human sporadic amyotrophic lateral sclerosis spinal cord tissues.[16][17] In addition to neurodegenerative diseases, P4HB level is upregulated in glioblastoma multiforme (GBM) (brain tumor). Inhibition of P4HB attenuates resistance to temozolomide, a standard GBM chemotherapeutic agent, via the PERK arm of endoplasmic reticulum stress response pathway.[18] Furthermore, heterozygous missense mutation in P4HB can cause Cole-Carpenter syndrome, a severe bone fragility disorder.[19]


P4HB has been shown to interact with UBQLN1,[20] ERO1LB[21][22] and ERO1L.[21][22]


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000185624 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000025130 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:".
  4. ^ "Mouse PubMed Reference:".
  5. ^ Shoulders CC, Brett DJ, Bayliss JD, Narcisi TM, Jarmuz A, Grantham TT, Leoni PR, Bhattacharya S, Pease RJ, Cullen PM (December 1993). "Abetalipoproteinemia is caused by defects of the gene encoding the 97 kDa subunit of a microsomal triglyceride transfer protein". Human Molecular Genetics. 2 (12): 2109–16. doi:10.1093/hmg/2.12.2109. PMID 8111381.
  6. ^ a b "Entrez Gene: P4HB procollagen-proline, 2-oxoglutarate 4-dioxygenase (proline 4-hydroxylase), beta polypeptide".
  7. ^ Galligan JJ, Petersen DR (July 2012). "The human protein disulfide isomerase gene family". Human Genomics. 6: 6. doi:10.1186/1479-7364-6-6. PMC 3500226. PMID 23245351.
  8. ^ Pajunen L, Jones TA, Goddard A, Sheer D, Solomon E, Pihlajaniemi T, Kivirikko KI (1991-01-01). "Regional assignment of the human gene coding for a multifunctional polypeptide (P4HB) acting as the beta-subunit of prolyl 4-hydroxylase and the enzyme protein disulfide isomerase to 17q25". Cytogenetics and Cell Genetics. 56 (3–4): 165–8. doi:10.1159/000133078. PMID 1647289.
  9. ^ Lumb RA, Bulleid NJ (December 2002). "Is protein disulfide isomerase a redox-dependent molecular chaperone?". The EMBO Journal. 21 (24): 6763–70. doi:10.1093/emboj/cdf685. PMC 139105. PMID 12485997.
  10. ^ Bastos-Aristizabal S, Kozlov G, Gehring K (May 2014). "Structural insight into the dimerization of human protein disulfide isomerase". Protein Science. 23 (5): 618–26. doi:10.1002/pro.2444. PMC 4005713. PMID 24549644.
  11. ^ Winter J, Klappa P, Freedman RB, Lilie H, Rudolph R (January 2002). "Catalytic activity and chaperone function of human protein-disulfide isomerase are required for the efficient refolding of proinsulin". The Journal of Biological Chemistry. 277 (1): 310–7. doi:10.1074/jbc.M107832200. PMID 11694508.
  12. ^ Tian G, Xiang S, Noiva R, Lennarz WJ, Schindelin H (January 2006). "The crystal structure of yeast protein disulfide isomerase suggests cooperativity between its active sites". Cell. 124 (1): 61–73. doi:10.1016/j.cell.2005.10.044. PMID 16413482.
  13. ^ Wang C, Li W, Ren J, Fang J, Ke H, Gong W, Feng W, Wang CC (July 2013). "Structural insights into the redox-regulated dynamic conformations of human protein disulfide isomerase". Antioxidants & Redox Signaling. 19 (1): 36–45. doi:10.1089/ars.2012.4630. PMID 22657537.
  14. ^ Bastos-Aristizabal S, Kozlov G, Gehring K (May 2014). "Structural insight into the dimerization of human protein disulfide isomerase". Protein Science. 23 (5): 618–26. doi:10.1002/pro.2444. PMC 4005713. PMID 24549644.
  15. ^ Atkin JD, Farg MA, Walker AK, McLean C, Tomas D, Horne MK (June 2008). "Endoplasmic reticulum stress and induction of the unfolded protein response in human sporadic amyotrophic lateral sclerosis". Neurobiology of Disease. 30 (3): 400–7. doi:10.1016/j.nbd.2008.02.009. PMID 18440237.
  16. ^ Walker AK, Farg MA, Bye CR, McLean CA, Horne MK, Atkin JD (January 2010). "Protein disulphide isomerase protects against protein aggregation and is S-nitrosylated in amyotrophic lateral sclerosis". Brain. 133 (Pt 1): 105–16. doi:10.1093/brain/awp267. PMID 19903735.
  17. ^ Uehara T, Nakamura T, Yao D, Shi ZQ, Gu Z, Ma Y, Masliah E, Nomura Y, Lipton SA (May 2006). "S-nitrosylated protein-disulphide isomerase links protein misfolding to neurodegeneration". Nature. 441 (7092): 513–7. doi:10.1038/nature04782. PMID 16724068.
  18. ^ Sun S, Lee D, Ho AS, Pu JK, Zhang XQ, Lee NP, Day PJ, Lui WM, Fung CF, Leung GK (May 2013). "Inhibition of prolyl 4-hydroxylase, beta polypeptide (P4HB) attenuates temozolomide resistance in malignant glioma via the endoplasmic reticulum stress response (ERSR) pathways". Neuro-Oncology. 15 (5): 562–77. doi:10.1093/neuonc/not005. PMC 3635523. PMID 23444257.
  19. ^ Rauch F, Fahiminiya S, Majewski J, Carrot-Zhang J, Boudko S, Glorieux F, Mort JS, Bächinger HP, Moffatt P (March 2015). "Cole-Carpenter syndrome is caused by a heterozygous missense mutation in P4HB". American Journal of Human Genetics. 96 (3): 425–31. doi:10.1016/j.ajhg.2014.12.027. PMC 4375435. PMID 25683117.
  20. ^ Ko HS, Uehara T, Nomura Y (September 2002). "Role of ubiquilin associated with protein-disulfide isomerase in the endoplasmic reticulum in stress-induced apoptotic cell death". The Journal of Biological Chemistry. 277 (38): 35386–92. doi:10.1074/jbc.M203412200. PMID 12095988.
  21. ^ a b Anelli T, Alessio M, Mezghrani A, Simmen T, Talamo F, Bachi A, Sitia R (February 2002). "ERp44, a novel endoplasmic reticulum folding assistant of the thioredoxin family". The EMBO Journal. 21 (4): 835–44. doi:10.1093/emboj/21.4.835. PMC 125352. PMID 11847130.
  22. ^ a b Mezghrani A, Fassio A, Benham A, Simmen T, Braakman I, Sitia R (November 2001). "Manipulation of oxidative protein folding and PDI redox state in mammalian cells". The EMBO Journal. 20 (22): 6288–96. doi:10.1093/emboj/20.22.6288. PMC 125306. PMID 11707400.

Further reading[edit]