Endoplasmic reticulum protein 29 (ERp29) is a chaperone protein that in humans is encoded by the ERP29 gene. [5]
Endoplasmic reticulum protein 29 (ERp29) is a chaperone protein that in humans is encoded by the ERP29 gene. [5]
ERp29 is a reticuloplasmin, a protein which resides in the lumen of the endoplasmic reticulum (ER). The protein shows sequence similarity to the protein disulfide-isomerase family. [6] However, it lacks the thioredoxin motif characteristic of this family, suggesting that this protein does not function as a disulfide isomerase. [6] The protein dimerizes and is thought to play a role in the processing of secretory proteins within the ER. Alternative splicing results in multiple transcript variants encoding different isoforms. [5]
In molecular biology, molecular chaperones are proteins that assist the conformational folding or unfolding of large proteins or macromolecular protein complexes. There are a number of classes of molecular chaperones, all of which function to assist large proteins in proper protein folding during or after synthesis, and after partial denaturation. Chaperones are also involved in the translocation of proteins for proteolysis.
Protein disulfide isomerase, or PDI, is an enzyme in the endoplasmic reticulum (ER) in eukaryotes and the periplasm of bacteria that catalyzes the formation and breakage of disulfide bonds between cysteine residues within proteins as they fold. This allows proteins to quickly find the correct arrangement of disulfide bonds in their fully folded state, and therefore the enzyme acts to catalyze protein folding.
Calnexin (CNX) is a 67kDa integral protein (that appears variously as a 90kDa, 80kDa, or 75kDa band on western blotting depending on the source of the antibody) of the endoplasmic reticulum (ER). It consists of a large (50 kDa) N-terminal calcium-binding lumenal domain, a single transmembrane helix and a short (90 residues), acidic cytoplasmic tail.
Tissue transglutaminase is a 78-kDa, calcium-dependent enzyme of the protein-glutamine γ-glutamyltransferases family. Like other transglutaminases, it crosslinks proteins between an ε-amino group of a lysine residue and a γ-carboxamide group of glutamine residue, creating an inter- or intramolecular bond that is highly resistant to proteolysis. Aside from its crosslinking function, tTG catalyzes other types of reactions including deamidation, GTP-binding/hydrolyzing, and isopeptidase activities. Unlike other members of the transglutaminase family, tTG can be found both in the intracellular and the extracellular spaces of various types of tissues and is found in many different organs including the heart, the liver, and the small intestine. Intracellular tTG is abundant in the cytosol but smaller amounts can also be found in the nucleus and the mitochondria. Intracellular tTG is thought to play an important role in apoptosis. In the extracellular space, tTG binds to proteins of the extracellular matrix (ECM), binding particularly tightly to fibronectin. Extracellular tTG has been linked to cell adhesion, ECM stabilization, wound healing, receptor signaling, cellular proliferation, and cellular motility.
Protein disulfide-isomerase A3 (PDIA3), also known as glucose-regulated protein, 58-kD (GRP58), is an isomerase enzyme. This protein localizes to the endoplasmic reticulum (ER) and interacts with lectin chaperones calreticulin and calnexin (CNX) to modulate folding of newly synthesized glycoproteins. It is thought that complexes of lectins and this protein mediate protein folding by promoting formation of disulfide bonds in their glycoprotein substrates.
Peptidyl-prolyl cis-trans isomerase B is an enzyme that is encoded by the PPIB gene. As a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family, this protein catalyzes the cis-trans isomerization of proline imidic peptide bonds, which allows it to regulate protein folding of type I collagen. Generally, PPIases are found in all eubacteria and eukaryotes, as well as in a few archaebacteria, and thus are highly conserved.
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. Unlike other prolyl 4-hydroxylase family proteins, this protein is multifunctional and acts as an oxidoreductase for disulfide formation, breakage, and isomerization. The activity of P4HB is tightly regulated. Both dimer dissociation and substrate binding are likely to enhance its enzymatic activity during the catalysis process.
Microsomal triglyceride transfer protein large subunit is a protein that in humans is encoded by the MTTP gene.
ERO1-like protein alpha is a protein that in humans is encoded by the ERO1L gene.
DnaJ homolog subfamily B member 11 is a protein that in humans is encoded by the DNAJB11 gene.
Enoyl Coenzyme A hydratase, short chain, 1, mitochondrial, also known as ECHS1, is a human gene.
15 kDa selenoprotein is a protein that in humans is encoded by the SEP15 gene. Two alternatively spliced transcript variants encoding distinct isoforms have been found for this gene.
Endoplasmic reticulum resident protein 44 (ERp44) also known as thioredoxin domain-containing protein 4 (TXNDC4) is a protein that in humans is encoded by the ERP44 gene.
Thioredoxin domain-containing protein 12 is a protein that in humans is encoded by the TXNDC12 gene.
ERO1-like protein beta is a protein that in humans is encoded by the ERO1LB gene.
Thioredoxin domain-containing protein 5 is a protein that in humans is encoded by the TXNDC5 gene.
Protein disulfide-isomerase TMX3 is an enzyme that in humans is encoded by the TMX3 gene.
Thioredoxins are small disulfide-containing redox proteins that have been found in all the kingdoms of living organisms. Thioredoxin serves as a general protein disulfide oxidoreductase. It interacts with a broad range of proteins by a redox mechanism based on reversible oxidation of 2 cysteine thiol groups to a disulfide, accompanied by the transfer of 2 electrons and 2 protons. The net result is the covalent interconversion of a disulfide and a dithiol.
ERp27 is a homologue of PDI, localised to the Endoplasmic Reticulum. The structure of ERp27 has been solved by both X-ray crystallography and NMR spectroscopy, showing it to be composed of two thioredoxin-like domains with homology to the non-catalytic b and b' domains of PDI. The function of ERp27 is unknown, but on the basis of its homology with PDI it is thought to possess chaperone activity.
Protein disulfide isomerase family A member 2 is a protein that in humans is encoded by the PDIA2 gene.
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