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Post-poly(Glu) cleavage and degradation modified by O-sulfated tyrosine: a novel post-translational processing mechanism.

Rehfeld J.F., Hansen C.P., Johnsen A.H.

Expression of bioactive peptides requires several modifications of the primary translation product. Gastrin, a vertebrate gut hormone, occurs in multiple forms, including a bioactive fragment of the predominant gastrin-17. Gastrin-17 is, however, without known cleavage sites. In order to identify the new site, we therefore isolated, from antral mucosa, fragments of gastrin-34 and -17 monitored by monospecific immunoassays. After three steps of reverse-phase chromatography, the short gastrins were identified as hepta-, hexa- and pentapeptide amides. By far the most abundant of these was tyrosine O-sulfated gastrin-6. The near complete sulfation contrasts with the larger gastrins, of which only half are sulfated. The longest N-terminal fragment of gastrin-34 was a hexadecapeptide without complementarity to the short gastrins. Instead, the predominant N-terminal fragment of gastrin-17 was the decapeptide complementary to gastrin-7. Therefore the novel processing site is the Glu10-Ala11 bond that follows a poly(Glu6-10) sequence. Moreover, gastrin-7 is apparently trimmed, with subsequent accumulation of sulfated gastrin-6. Consequently, O-sulfated tyrosine ensures production of a new hormone which stimulates gastric acid secretion as potently as gastrin-17.

EMBO J. 14:389-396(1995) [PubMed] [Europe PMC]

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