P4HB

This multifunctional protein catalyzes the formation, breakage and rearrangement of disulfide bonds. At the cell surface, seems to act as a reductase that cleaves disulfide bonds of proteins attached to the cell. May therefore cause structural modifications of exofacial proteins. Inside the cell, seems to form/rearrange disulfide bonds of nascent proteins. At high concentrations and following phosphorylation by FAM20C, functions as a chaperone that inhibits aggregation of misfolded proteins. At low concentrations, facilitates aggregation (anti-chaperone activity). May be involved with other chaperones in the structural modification of the TG precursor in hormone biogenesis. Also acts as a structural subunit of various enzymes such as prolyl 4-hydroxylase and microsomal triacylglycerol transfer protein MTTP. Receptor for LGALS9; the interaction retains P4HB at the cell surface of Th2 T helper cells, increasing disulfide reductase activity at the plasma membrane, altering the plasma membrane redox state and enhancing cell migration.

Phosphorylation of Ser-359 by FAM20C is induced by endoplasmic reticulum stress and results in a functional switch from oxidoreductase to molecular chaperone. It also promotes interaction with ERN1.

Belongs to the protein disulfide isomerase family.

• Endoplasmic reticulum
• Endoplasmic reticulum lumen
• Melanosome
• Cell membrane
• Peripheral membrane protein
• Highly abundant. In some cell types, seems to be also secreted or associated with the plasma membrane, where it undergoes constant shedding and replacement from intracellular sources. Localizes near CD4-enriched regions on lymphoid cell surfaces. Colocalizes with MTTP in the endoplasmic reticulum.

PDIA1, P4HB, Protein disulfide-isomerase, PDI, Prolyl 4-hydroxylase subunit beta, p58

• swissprot:Q8R4U2

Proteins

Metabolism

57010Da