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OVINE PROINSULIN – IDENTIFICATION AND IMMUNOLOGICAL SIMILARITY TO BOVINE PROINSULIN
Author(s) -
Ellis M Jane,
Donald RA,
Arcus AC,
Livesey JH
Publication year - 1974
Publication title -
australian journal of experimental biology and medical science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.999
H-Index - 104
eISSN - 1440-1711
pISSN - 0004-945X
DOI - 10.1038/icb.1974.11
Subject(s) - proinsulin , sephadex , radioimmunoassay , insulin , chemistry , medicine , endocrinology , biochemistry , chromatography , biology , enzyme
Summary Ovine proinsulin has been partially purified and characterised and shown to be immunologically similar to bovine proinsulin. Gel filtration of ovine insulin crystals followed by insulin radioimmunoassay of the effluent fractions indicated a small peak of insulin immunoreactivity characterised by a higher molecular weight than insulin. This material co‐eluted with porcine proinsulin tracer when refiltered on Sephadex, and on poly‐acrylamide gel electrophoresis was shown to contain a protein component corresponding to porcine proinsulin. Tryptic digestion converted both the immunoreactivity and the radioactivity of 125 I‐labelled crude ovine proinsulin from the proinsulin to the insulin elution position on Sephadex. Following reduction of the disulphide bonds with dithiothreitol, the labelled material partially retained a single‐chain form as expected for proinsulin, but showed some of the cleavage characteristics of insulin or insulin‐like conversion intermediates. In a specific bovine proinsulin radioimmunoassay, the crude ovine proinsulin exhibited parallelism and considerable cross‐reactivity whereas ovine insulin and porcine proinsulin showed little cross‐reaction. These results suggest that there is an insulin precursor, proinsulin, in sheep as reported in other species. Furthermore, the immunological properties of ovine proinsulin imply that its molecular structure is more closely related to that of bovine proinsulin than porcine proinsulin.