A novel 53-kDa polypeptide from chicken embryo.
We have isolated from chicken embryos a novel 53-kDa protein possessing properties which are similar, but not identical to the 55-kDa PDI polypeptide from chicken embryos. The novel 53-kDa polypeptide copurifies with PDI, but is separated by ion-exchange chromatography. The novel 53-kDa polypeptide cross-reacts strongly with antibodies specific for bovine PDI and cross-reacts to varying degrees with six different preparations of antibodies specific for chicken PDI which is identical to the beta-subunit of chicken prolyl 4-hydroxylase. Anti-bovine PDI immunoglobulins selected by the purified 53-kDa polypeptide react with bovine PDI but not with the beta-subunit of prolyl 4-hydroxylase, suggesting that the 53-kDa polypeptide shares epitopes with bovine PDI but not with the chicken prolyl 4-hydroxylase beta-subunit. Amino acid compositional analysis of the purified polypeptide yielded unique data when compared to PDI and other PDI-like polypeptides. Edman degradation from the N terminus of the 53-kDa polypeptide yields a sequence very different from the N terminus of PDI. This sequence is unique when compared to all entries in available databases. A 20-residue sequence of an internal cyanogen bromide fragment of the 53-kDa polypeptide gives a nearly identical match with human beta-endorphin. The 53-kDa polypeptide is capable of cleaving the disulphides of insulin under conditions where PDI is active. The periodic acid-Schiff assay failed to detect bound carbohydrate. These observations support evidence for a family of PDI-like proteins in chicken embryo and suggest that PDI activity is not confined to only one protein.
Bassuk
J A
JA
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854.
Berg
R A
RA
D000595:Amino Acid Sequence; D000818:Animals; D002642:Chick Embryo; D003429:Cross Reactions; D006801:Humans; D007136:Immunoglobulins / Q000276:immunology / Q000302:isolation & purification; D007535:Isomerases / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification; D010455:Peptides / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D011393:Procollagen-Proline Dioxygenase / Q000302:isolation & purification; D019704:Protein Disulfide-Isomerases; D011817:Rabbits / Q000276:immunology; D012689:Sequence Homology, Nucleic Acid; D001615:beta-Endorphin / Q000235:genetics
D007136:Immunoglobulins; D046911:Macromolecular Substances; D010446:Peptide Fragments; D010455:Peptides; D001615:beta-Endorphin; D011393:Procollagen-Proline Dioxygenase; D007535:Isomerases; D019704:Protein Disulfide-Isomerases