Development of a biotinylated analog of substance P for use as a receptor probe.

The development of a biotinylated substance P (SP) analog for use as a receptor probe is reported. The lysine in position 3 of SP was substituted by arginine and an amino terminal extension (NTE-SP) was added consisting of Lys-Tyr-Gly-Gly-Gly-Gly-Gly-Gly. Biotinylation of the N-terminal lysine was performed. The biotinylated peptide was purified by high performance liquid chromatography and characterized by mass spectral analysis. Binding studies using human IM-9 lymphoblasts with the biotinylated SP analog (biotin-NTE[Arg3]SP) and native SP yielded dissociation curves which were identical. In addition, the biotinylated SP analog retained functional activity similar to that of native SP in altering intracellular calcium concentration of Fura-2 loaded isolated rabbit colonic myocytes. Applicability of the SP receptor probe was demonstrated by using the streptavidin-peroxidase detection system to identify SP receptors on human IM-9 lymphoblasts. In conclusion, a biotinylated SP analog has been developed which retains the functional characteristics of the native peptide and is a useful and versatile probe for receptor studies.