QSOX1

{{Short description|Protein-coding gene in the species Homo sapiens}}

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Quiescin sulfhydryl oxidase 1 is an enzyme that in humans is encoded by the QSOX1 gene.{{cite journal | vauthors = Coppock DL, Cina-Poppe D, Gilleran S | title = The quiescin Q6 gene (QSCN6) is a fusion of two ancient gene families: thioredoxin and ERV1 | journal = Genomics | volume = 54 | issue = 3 | pages = 460–468 | date = December 1998 | pmid = 9878249 | doi = 10.1006/geno.1998.5605 | doi-access = free }}{{cite journal | vauthors = Coppock DL, Kopman C, Scandalis S, Gilleran S | title = Preferential gene expression in quiescent human lung fibroblasts | journal = Cell Growth & Differentiation | volume = 4 | issue = 6 | pages = 483–493 | date = June 1993 | pmid = 8396966 }}{{cite web | title = Entrez Gene: QSCN6 quiescin Q6| url = https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=5768}}

This gene encodes an enzyme that is localized primarily to the Golgi apparatus and secreted fluids.{{cite journal | vauthors = Kodali VK, Thorpe C | title = Oxidative protein folding and the Quiescin-sulfhydryl oxidase family of flavoproteins | journal = Antioxidants & Redox Signaling | volume = 13 | issue = 8 | pages = 1217–1230 | date = October 2010 | pmid = 20136510 | doi = 10.1089/ars.2010.3098 | pmc = 2959182 }} QSOX1 is a multi-domain disulfide catalyst. Unlike other disulfide catalysts, QSOX1 can both generate disulfides de novo and catalyze dithiol/disulfide exchange. The de novo disulfide bond formation is catalyzed by the ERV1 domain that contains a FAD co-factor that allows depositions of electrons onto the terminal electron acceptor, typically molecular oxygen. The dithiol/disulfide exchange is catalyzed by the thioredoxin domain. The two domains are linked together by a flexible linker that allows the thioredoxin domain to first interact with the substrate protein and then regenerate by ERV1 domain.{{cite journal | vauthors = Alon A, Grossman I, Gat Y, Kodali VK, DiMaio F, Mehlman T, Haran G, Baker D, Thorpe C, Fass D | title = The dynamic disulphide relay of quiescin sulphydryl oxidase | journal = Nature | volume = 488 | issue = 7411 | pages = 414–418 | date = August 2012 | pmid = 22801504 | doi = 10.1038/nature11267 | pmc = 3521037 }}

QSOX1 gene expression is induced as fibroblasts begin to exit the proliferative cycle and enter quiescence,{{cite journal | vauthors = Coppock DL, Cina-Poppe D, Gilleran S | title = The quiescin Q6 gene (QSCN6) is a fusion of two ancient gene families: thioredoxin and ERV1 | journal = Genomics | volume = 54 | issue = 3 | pages = 460–468 | date = December 1998 | pmid = 9878249 | doi = 10.1006/geno.1998.5605 | doi-access = free }}{{cite journal | vauthors = Coppock DL, Kopman C, Scandalis S, Gilleran S | title = Preferential gene expression in quiescent human lung fibroblasts | journal = Cell Growth & Differentiation | volume = 4 | issue = 6 | pages = 483–493 | date = June 1993 | pmid = 8396966 | url = https://aacrjournals.org/cgd/article/4/6/483/706409/Preferential-gene-expression-in-quiescent-human }} suggesting that this gene plays an important role in growth regulation. In fibroblasts QSOX1 is required for normal incorporation of laminin into the extracellular matrix, and thereby for normal cell-cell adhesion and cell migration.{{cite journal | vauthors = Ilani T, Alon A, Grossman I, Horowitz B, Kartvelishvily E, Cohen SR, Fass D | title = A secreted disulfide catalyst controls extracellular matrix composition and function | journal = Science | volume = 341 | issue = 6141 | pages = 74–76 | date = July 2013 | pmid = 23704371 | doi = 10.1126/science.1238279 }}

Two transcript variants encoding two different isoforms have been found for this gene.* {{cite journal | vauthors = Radom J, Colin D, Thiebault F, Dognin-Bergeret M, Mairet-Coello G, Esnard-Feve A, Fellmann D, Jouvenot M | title = Identification and expression of a new splicing variant of FAD-sulfhydryl oxidase in adult rat brain | journal = Biochimica et Biophysica Acta | volume = 1759 | issue = 5 | pages = 225–233 | date = May 2006 | pmid = 16806532 | doi = 10.1016/j.bbaexp.2006.04.008 }} The two isoforms have different tissue distribution and in addition isoform 1 has a transmembrane helix in the carboxy terminal while isoform 2 is a secreted soluble protein.