A simple procedure for the isolation of protein disulphide-isomerase.

A two-step procedure is described for the purification of protein disulphide-isomerase (PDI). This procedure is based on the previous finding that the beta-subunit of the prolyl 4-hydroxylase tetramer (alpha 2 beta 2) is identical with PDI [Koivu, Myllylä, Helaakoski, Pihlajaniemi, Tasanen & Kivirikko (1987) J. Biol.

Disulfide bonding as a determinant of the molecular composition of types I, II and III procollagen.

Procollagen molecules have amino-terminal and carboxy-terminal propeptides at the respective ends of the collagenous triple helix. The carboxy-terminal propeptides enhance and direct the association of pro alpha-chains into procollagen molecules, but the mechanism of this registration function is still obscure. A hypothesis concerning the function of disulfide bonding in the assembly of types I, II and III procollagen is put forward here.

A single polypeptide acts both as the beta subunit of prolyl 4-hydroxylase and as a protein disulfide-isomerase.

A single polypeptide is shown to act both as the beta subunit of the proline hydroxylase (EC 1.14.11.

Interchain disulfide bond formation in types I and II procollagen. Evidence for a protein disulfide isomerase catalyzing bond formation.

The assembly of reduced pro-alpha chains of type I and type II procollagen into the native triple-helical molecule was examined in vitro in the presence and absence of pure protein disulfide isomerase. The data clearly indicates that protein disulfide isomerase is able to accelerate the formation of native interchain disulfide bonds in these procollagens. It takes about 6 min after disulfide bonding before triple-helical molecules exist, while the time required to produce triple-helical type I procollagen in the presence of protein disulfide isomerase is 9.

Molecular cloning of the beta-subunit of human prolyl 4-hydroxylase. This subunit and protein disulphide isomerase are products of the same gene.

Prolyl 4-hydroxylase (EC 1.14.11.