Immunochemical specificity of myosin light chains from mackerel ordinary and dark muscles

Five light chains were isolated from the ordinary and dark muscle myosins of mackerel Pneumatophorus japonicus japonicus, by a method consisting of DTNB and urea treatments, followed by DEAE-cellulose chromatography. Some physicochemical and immunochemical properties of the light chains thus obtained were analyzed. A1, A2, and DTNB light chains from ordinary muscle myosin resembled one another in ultraviolet absorption spectrum, as did D1 and D2 light chains from dark muscle myosin. However, the absorption spectra of the former three differed from those of the latter two. Amino acid compositions of A1 and A2 light chains resembled each other, except for a few amino acids such as lysine, proline, and alanine. Tryptophan was detected only in DTNB light chain. D1 and D2 light chains showed general similarity, except for a remarkably higher proline content in D1. Anti-A1 (or anti-A2) antiserum exhibited a cross-reaction against A2 (or A1) in both immunoelectrophoresis and ELISA, indicating an immunochemical similarity of these two alkali light chains. No precipitin line appeared when anti-A1 or anti-A2 antiserum was diffused against DTNB light chain in immunoelectrophoresis. In ELISA, however, each pair showed cross-reactivity values as high as 50-80%, values which were rather higher than those obtained with heterologous alkali light chains (10-40%). Anti-DTNB light chain antiserum reacted with either alkali light chain in both methods. Anti-D1 antiserum cross-reacted against D2, and anti-D2 antiserum did against D1. These myosin light chains exhibited a high immunochemical tissue-specificity.