Sequence analysis of cloned cDNA for rat substance P precursor: existence of a third substance P precursor

The sequence of the mRNA for the rat substance P precursor (preprotachykinin A) has been elucidated by molecular cloning and sequence analysis. The deduced amino acid sequence of rat preprotachykinin A indicates that it contains both substance P and substance K but differs in the sequence organization from either bovine alpha- or beta-preprotachykinin A reported previously. The existence of the bovine mRNA for the third preprotachykinin A has thus been examined and evidenced by the isolation of the corresponding cDNA clone. This mRNA, named gamma-preprotachykinin A mRNA, deletes the sequence precisely corresponding to the exon 4 sequence of the preprotachykinin A gene. Thus, alternative RNA splicing in the expression of the single preprotachykinin A gene results in the generation of three different forms of the preprotachykinin A mRNAs.