Anti-P4HB Antibody Picoband® Fluoro488 Conjugated

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. 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.

Isoform 2 and isoform 3 function as proton-gated sodium channels; they are activated by a drop of the extracellular pH and then become rapidly desensitized. The channel generates a biphasic current with a fast inactivating and a slow sustained phase. Has high selectivity for sodium ions and can also transport lithium ions with high efficiency. Isoform 2 can also transport potassium, but with lower efficiency. It is nearly impermeable to the larger rubidium and cesium ions. Isoform 3 can also transport calcium ions. Mediates glutamate-independent Ca2+entry into neurons upon acidosis. This Ca2+overloading is toxic for cortical neurons and may be in part responsible for ischemic brain injury. Heteromeric channel assembly seems to modulate channel properties. Functions as a postsynaptic proton receptor that influences intracellular Ca2+concentration and calmodulin-dependent protein kinase II phosphorylation and thereby the density of dendritic spines. Modulates activity in the circuits underlying innate fear.

1. Cheng, S. Y., Gong, Q. H., Parkinson, C., Robinson, E. A., Appella, E., Merlino, G. T., Pastan, I. The nucleotide sequence of a human cellular thyroid hormone-binding protein present in endoplasmic reticulum. J. Biol. Chem. 262: 11221-11227, 1987. 2. Koivu, J., Myllyla, R., Halaakoski, T., Pihlajaniemi, T., Tasanen, K., Kivirikko, K. I. A single polypeptide acts both as the beta subunit of prolyl 4-hydroxylase and as a protein disulfide-isomerase. J. Biol. Chem. 262: 6447-6449, 1987. 3. Mezghrani, A., Fassio, A., Benham, A., Simmen, T., Braakman, I., Sitia, R. Manipulation of oxidative protein folding and PDI redox state in mammalian cells. EMBO J. 20: 6288-6296, 2001.