Mapping of fish myosin light chains by two-dimensional gel electrophoresis

1. Myosins were prepared from the ordinary muscle of 16 fish species as well as from rabbit fast muscle, and light chain subunits [alkali light chains A1, A2 and DTNB (5,5'-dithio-bis-2-nitrobenzoate) light chain] were separated on two-dimensional gel electrophoresis in combination with isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. 2. A1 light chains showed mol. wts ranging from 21,000 to 22,900 and isoelectric points ranging from 4.51 to 4.62. DTNB light chains were spotted in a narrow area, with a mol. wt range of 16,800-17,600 and an isoelectric point range of 4.48-4.55. On the other hand, A2 light chains were most species-specific, with a mol. wt range of 14,000-19,500 and an isoelectric point range of 4.31-4.46. 3. It was suggested that the lower species-specificity in A1 as opposed to A2 is accounted for by the addition of an N-terminal peptide ("difference peptide") in the former. The properties and possible role of this peptide are discussed.