Identification of a 63-kDa serum protein that binds somatostatin and gastrin-releasing peptide but not bombesin.
A 63-kDa serum protein was identified that bound somatostatin and gastrin-releasing peptide (GRP) but not bombesin. The 63-kDa protein was detected by its ability to compete with the receptor for GRP in a receptor binding assay. This interaction could be inhibited by the addition of somatostatin, producing a higher and more accurate calculated affinity for the binding of GRP to its receptor. Somatostatin did not affect the affinity of the receptor for bombesin. Specificity of the 63-kDa protein for analogs of somatostatin, GRP, and bombesin was determined by competition with 125I-GRP and 125I-somatostatin. A tripeptide motif consisting of an aryl-hydrophobic-basic amino-acid structure in residues 15-17 of GRP (Tyr-Pro-Arg) and residues 7-9 of somatostatin (Phe-Trp-Lys) was implicated in binding. This tripeptide binding motif is not present in bombesin. That residues 15-17 of GRP are highly conserved suggests that its interaction with the 63 kDa serum protein may be physiological.
Fanger
B O
BO
Marion Merrell Dow Research Institute, Cincinnati, OH 45215-6300.
Wade
A C
AC
Cashman
E A
EA
Cardin
A D
AD
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D001798:Blood Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D001839:Bombesin / Q000378:metabolism*; D019886:Gastrin-Releasing Peptide; D051379:Mice; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013004:Somatostatin / Q000378:metabolism*
D001798:Blood Proteins; D010455:Peptides; D013004:Somatostatin; D019886:Gastrin-Releasing Peptide; D001839:Bombesin