Fish myosin alkali light chains originate from two different genes.

We have determined the amino acid sequences of mullet white skeletal muscle myosin alkali light chains, LC1 and LC3. These are the first available fish myosin sequences. There are 29 differences between the mullet LC1 and LC3 sequences, spread throughout all regions of their polypeptide chains, leading us to conclude that fish myosin alkali light chains originate from two different genes. This finding is in sharp contrast to all previous studies on vertebrate fast skeletal muscle myosins, which showed that in birds and mammals LC1 and LC3 are produced from a single gene by alternative RNA transcription and splicing, yielding proteins which differ only in their N-terminal segments.