Identification of cellular prosomatostatin and nonsomatostatin peptides derived from its amino terminus.
Rat prosomatostatin was isolated from a somatostatin-producing cell line and was partially microsequenced. This indicated the amino terminal structure of cellular prosomatostatin and implied a 92-amino acid sequence for the somatostatin precursor. Based on the structure for cellular prosomatostatin, a peptide was synthesized and used to develop a radioimmunoassay directed toward the amino terminal portion of prosomatostatin. This assay has revealed two peptides containing the amino-terminal portion of prosomatostatin in a somatostatin-secreting CA-77 rat medullary thyroid carcinoma cell line. These two peptides - MW 4000 and 8000 daltons - lack somatostatin immunoreactivity. Thus, processing of prosomatostatin occurs both at the amino and carboxyl regions. These results open the way for elucidation of the structure, function and metabolism of non-somatostatin peptides derived from the amino terminus of prosomatostatin.
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis*; D011498:Protein Precursors / Q000032:analysis*; D011863:Radioimmunoassay; D051381:Rats; D013004:Somatostatin / Q000032:analysis*; D013964:Thyroid Neoplasms / Q000032:analysis*
D010446:Peptide Fragments; D011498:Protein Precursors; D013004:Somatostatin; C028456:prosomatostatin