Quantitation and Characterization of Peptides from the C-Terminal Flanking Region of Rat and Bovine Preprotachykinins

Sequence analysis of cDNAs has shown that the biosynthetic precursors of substance P (alpha-, beta-, and gamma-preprotachykinins) contain a common amino acid sequence in the C-terminal flanking region that has not been conserved between species. Antisera have been raised against the synthetic peptide Tyr-Glu-Arg-Ser-Ala-Met-Gln-Asn-Tyr-Glu, which represents rat beta-preprotachykinin-(117-126)-peptide, and used in radioimmunoassays. Antiserum R50 reacted strongly with C-flanking peptides in extracts of rat and bovine tissues whereas antiserum GP-4 reacted only with the rat peptides. The primary structure of the predominant molecular form of preprotachykinin C-flanking peptide in an extract of bovine corpus striatum was established as: Ala-Leu-Asn-Ser-Val5-Ala-Tyr-Glu-Arg-Ser10-Val-Met-Gln-Asp-Tyr1 5-Glu. This sequence represents beta-preprotachykinin-(111-126)-peptide which is equivalent to gamma-preprotachykinin-(96-111)-peptide. A C-flanking peptide with similar chromatographic properties was identified in extracts of rat brain and gut together with a second immunoreactive component that may represent a fragment or a posttranslationally modified variant. A peptide corresponding to the 37-amino-acid residue C-flanking peptide derived from alpha-preprotachykinin was not detected in the extracts as expected from the known low abundance of alpha-preprotachykinin mRNA in rat brain and gut.