Bacterial peptides with C-terminal similarities to bovine neurotensin

Using radioimmunoassay, peptides resembling the C-terminal region of bovine neurotensin (NT) have been demonstrated in acid/acetone extracts of Rhodopseudomonas palustris, Escherichia coli, and Caulaobacter crescentus. The NT-like bacterial components were shown to behave as peptides of small molecular weight (less than 2000) which were stable to acid and heat but labile to proteolytic digestion. In the radioimmunoassay toward NT they displayed dose-response curves parallel to standard and gave results indicating a competitive type of interaction with NT binding sites on antibody. The bacterial extracts did not register in a control radioimmunoassay toward rat luteinizing hormone. Some of the NT-like immunoreactivity could also be bound to an retrieved from anti-NT-antibody-Sepharose preparations. Since the C-terminal region of NT constitutes its biologically active core, these results suggest that presence of biologically important congeners of NT in bacteria.