Isolation and Structure of Cat Superfast Myosin Light Chain-2 cDNA and Evidence for the Identity of Its Human Homologue

Abstract A full-length cDNA clone coding for superfast myosin light chain-2 (MyLC2) was isolated from an expression cDNA library prepared from cat masseter muscle and was fully characterized. The deduced amino acid sequence shares 58% overall identity with limb fast MyLC2, whereas homologies of the latter among higher vertebrates show 90% identity, indicating that superfast MyLC2 has diverged considerably from limb fast MyLC2 during evolution. Superfast MyLC2 cDNA has 89% nucleotide homology and 93% amino acid homology with a published novel human MyLC2 (MYL5), suggesting that MYL5 is a human homologue of the cat superfast MyLC2. Hybridization of a superfast MyLC2 isoform-specific probe reveals that expression of superfast MyLC2 in cat is confined to jaw-closing muscles. In conclusion, the present paper describes for the first time the cloning of a superfast myosin light chain coding sequence.