Characterization of a gene encoding a Pichia pastoris protein disulfide isomerase

Protein disulphide isomerases belong to the thioredoxin superfamily of protein-thiol oxidoreductases that have two double-cysteine redox-active sites and take part in protein folding in the endoplasmic reticulum (ER). We report here the cloning of a Pichia pastoris genomic DNA fragment (2919 bp) that encodes the full length of a protein disulphide isomerase (PpPDI). The deduced amino acid sequence of PDI consists of 517 residues and carries the two characteristic PDI-type redox-active domains -CGHC-, separated by 338 residues, and two potential N-glycosylation sites. The N-terminal end forms a putative signal sequence, and an acidic C-terminal region represents a possible calcium-binding domain. Together with the -HDEL ER retrieval sequence at the C-terminus, these features indicate that the gene encodes a redox-active ER-resident protein disulphide isomerase. The nucleotide sequence, which also contains two other open reading frames, has been submitted to the EMBL Nucleotide Sequence Database, Accession No. AJ302014. (C) 2001 Academic Press.