Protein disulfide-isomerase subunit

Kivirikko, K.I. and Pihlajaniemi, T. (1998) Collagen hydroxylases and the protein disulfide isomerase subunit of prolyl 4-hydroxylases. Advances inEnzymology and Related Areas of Molecular Biology 72, 325-400. 

Kivirikko KI, Myllyhaiju J. Prolyl 4-hydroxylases and their protein disulfide isomerase subunit. Matrix Biol 1998 16 357-368. 

Veijola, J., Koivunen, P., Annunen, P., Pihlajaniemi, T. and Kivirikko, K. (1994) Cloning, baculovirus expression, and characterization of the alpha-subunit of prolyl 4-hydroxylase from the nematode Caenorhabditis elegans - this alpha-subunit forms an active alpha-beta dimer with the human protein disulfide-isomerase beta-subunit. Journal of Biological Chemistry 269, 26746-26753. 

MTP is responsible for the transfer of TGs and cholesteryl esters from the endoplasmic reticulum (ER) to lipoprotein particles (VLDL in hepatocytes in the liver and chylomicrons in endocytes in the intestine) for secretion [52]. It is a heterodimer consisting of a unique large subunit essential for lipid transfer encoded by the mttp gene and a smaller subunit, the ubiquitous ER enzyme protein disulfide isomerase [53]. 

Cydophilin A Ferritin light subunit GAPDH Galectin-1 Glutathione S-transferase MnSOD Protein disulfide isomerase A3 precursor... 

The hydroxylation of specific Pro residues in procollagen, the precursor of collagen, requires the action of the enzyme prolyl 4-hydroxylase. This enzyme (Mt 240,000) is an a2/32 tetramer in all vertebrate sources. The proline-hydroxylating activity is found in the a subunits. (Researchers were surprised to find that the )3 subunits are identical to the enzyme protein disulfide isomerase (PDI p. 152) these subunits do not participate in the prolyl hydroxylation activity.) Each a subunit contains one atom of nonheme iron (Fe2+), and the enzyme is one of a class of hydroxylases that require a-ketoglutarate in their reactions. 

In ABL, an early step in apoB lipoprotein assembly shared by intestinal and liver cells is defective. The net result is near absence of all plasma apoB lipoproteins. ApoB synthesis from a mRNA transcript occurs, but its successful assembly into the mature lipoprotein particle does not. The inability to assemble apoB into lipoproteins was shown to be due to a defect in the mttp gene in affected individuals (Wetterau et al., 1992). Its translational product is an 894-amino acid, 97-kd, polypeptide that exists in the ER complexed with a 55-kd protein disulfide isomerase which is believed to maintain solubility, physiologic activity, and ER retention of the 97-kd peptide. The heterodimeric complex of the 97-kd and 55-kd subunits is referred to as microsomal triglyceride transfer protein (MTP) (Wetterau et al., 1992). 

Norgaard P, Westphal V, Tachibana C, Alsoe L, Holst B, Winther JR (2001) Functional differences in yeast protein disulfide isomerases. J Cell Biol 152 553 562 Oliver JD, Roderick HL, Llewellyn DH, High S (1999) ERp57 functions as a subunit of specific complexes formed with the ER lectins calreticulin and calnexin. Mol Biol Cell 10 2573-2582 Oliver JD, van der Wal FJ, Bulleid NJ, High S (1997) Interaction of the thiol-dependent reductase ERp57 with nascent glycoproteins. Science 275 86-88... 

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