Isolation and structure of the rat gene encoding troponin I(slow).

Troponin I is a myofibrillar protein involved in the Ca(2+)-mediated regulation of actomyosin ATPase activity. We report here the isolation and characterization of the gene coding for the slow-muscle-specific isoform of the rat troponin I polypeptide (TpnI). Using restriction mapping, PCR mapping and partial DNA sequencing, we have determined the exon/intron arrangement of this gene. The transcription unit is 10.5-kb long and contains nine exons ranging in size from 4 bp to 330 bp. The rat TpnI(slow) gene is interrupted by large intervening sequences; a 3.3-kb intron separates the 5' untranslated exons from the protein-coding exons. Comparison of the structure of rat TpnI(slow) with that of quail TpnI(fast) reveals that they have a similar intron/exon organization. The 5' untranslated region of the rat gene contains an additional exon, otherwise, the positions of introns and coding exons map to essentially identical regions in both genes.