Cloning and Expression of Rat and Human Tachykinin Genes
We have cloned the rat and human genes encoding substance P. Their structure (Fig. 1) is very similar to that of the bovine gene , i. e., they have seven exons with the third exon encoding substance P and the sixth exon encoding substance K. The exons (2–6) which have predominantly coding sequences are well conserved (89–99%) in nucleotide sequence while the exons containing predominantly noncoding sequences (1 and 7) are less conserved (57–72%). Although the introns are well conserved in size there is little sequence conservation between the rat and human introns. The region immediately in front of the first exon, i.e., the presumptive promoter region, has an unusually long (360 bases) conserved (84%) region. The precursor proteins encoded by the genes are 130 (rat) or 129 (human) amino acids and differ at only 6 amino acid positions. The 25 amino acids (excluding the Lys-Arg sequences at both ends) which are located between the substance P and substance K peptides are completely conserved between rat and human and have only a single conservative (isoleucine to leucine) substitution in the bovine precursor. This conservation suggests that the intervening peptide has an important function.
KeywordsNoncoding Sequence Bovine Gene Tissue Specific Fashion Human Intron Single Conservative