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

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Abstract
Sequence analysis of cDNAs has shown that the biosynthetic precursors of substance P (α-,β-, and γ-prepro-tachykinins) 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 β-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 prepro tachykinin 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-Tyr15-GIu. This sequence represents β-preprotachykinin-(111-126)-peptide which is equivalent to γ-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 α-preprotachykinin was not detected in the extracts as expected from the known low abundance of SaL-preprotachykinin mRNA in rat brain and gut.