Isolation and Characterization of a cDNA Encoding for Preprosomatostatin Containing [Tyr 7, Gly 10]-Somatostatin-14 from the Endocrine Pancreas of Rainbow Trout, Oncorhynchus mykiss

Abstract

Somatostatins are a diverse group of peptides known to influence various aspects of growth and metabolism of vertebrates. In order to further our understanding of the physiological roles of somatostatins in fish, we initiated an analysis of somatostatin gene structure and expression in rainbow trout pancreas. Using rapid amplification of cDNA ends polymerase chain reaction, we have isolated, cloned, and sequenced a novel cDNA derived from pancreatic total RNA. Sequence analysis revealed a 624-bp cDNA containing the complete 5′-untranslated region with a single initiation site 107 bases from the most 5′ end and a single putative polyadenylation site 13 bases from the most 3′ end that was terminated with a polyadenylated tail. The deduced protein is a 115-amino-acid preprosomatostatin molecule with [Tyr 7, Gly 10]-somatostatin-14 at the C-terminus of the coding region, making the rainbow trout precursor a member of the preprosomatostatin II family. Based on the location of putative cleavage sites, we propose that rainbow trout pancreatic preprosomatostatin II is processed to yield a 28-amino-acid and/or, possibly, a 14-amino-acid somatostatin II molecule. The results also suggest that there has been limited conservation of the preprosomatostatin II gene family among teleosts.