Affiliation:
1. Department of Anatomy, Emory University School of Medicine Atlanta, Georgia 30322 Marine Biological Laboratory Woods Hole, Massachusetts 02543
2. Peptide Biology Laboratory at the Salk Institute for Biological Studies LaJolla, California 92037
Abstract
The purpose of this study was to determine if the somatostatin in pancreatic islets is synthesized via a precursor-product pathway. Anglerfish islets were subjected to pulse-chase incubations with 3H-tryptophan 14C-isoleucine. Islet extracts were subjected to gel filtration on Bio-Gel P-10. During chase incubations in the presence of cycloheximide, a linear increase of 3H-radioactivity in the somatostatin-containing portion of the eluate was observed while 14C-label did not accumulate in this region. A concomitant diminution of both 3H- and 14C- radioactivity in the 8-15-kilodalton region of the eluate occurred during the chase periods, suggesting a transfer of label from larger to smaller peptides. The labeled peptides found in the 8-15-kilodalton range were subjected to treatment with 8 M urea, 8 M urea−5% thioglycolic acid, 6 M guanidine hydrochloride, and 8 M guanidine hydrochloride−5% thioglycol. No appreciable loss of radioactivity was apparent after any of these treatments. Incubation of these same peptides with cell-free supernate from unlabeled islet tissue or with trypsin yielded a tryptophan-labeled peptide having the molecular size, electrophoretic mobility, and immunoreactivity of anglerfish and synthetic somatostatin. These results suggest that a precursor peptide having a molecular size near that of proinsulin is used in the biosynthesis of somatostatin.
Publisher
American Diabetes Association
Subject
Endocrinology, Diabetes and Metabolism,Internal Medicine
Cited by
87 articles.
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