Molecular cloning, sequencing and expression of an isoform of cardiac alpha-tropomyosin from the Mexican axolotl (Ambystoma mexicanum).

The cDNA for alpha-tropomyosin (TM) was cloned by the polymerase chain reaction (PCR) from a lambda gt11 library constructed with mRNA from juvenile axolotl heart tissues. Subsequently, the nucleotide sequence of the cDNA was determined. This is the first reported cDNA for axolotl alpha-tropomyosin. Comparative analyses of the deduced amino acid sequence of this cDNA with Xenopus skeletal muscle alpha-tropomyosin sequences indicate that the axolotl heart cDNA has 93% and 96% homology in the regions of amino acids 39-80 (exon 2b) and 258-284 (exon 9a), respectively. However, there is about 86.55% homology at the nucleic acid level (coding region) and 97.5% homology at the amino acid level with that of Xenopus skeletal muscle alpha-tropomyosin cDNA. Northern blot analyses with polyA+ RNA from juvenile heart suggest the presence of at least two different transcripts for alpha-tropomyosin in axolotl heart. The results of 3'-RACE concur with those of northern blot analyses.