Isolation of light chains from ordinary and dark muscle myosins of mackerel.

Abstract

Light chains were dissociated by DTNB and/or urea treatments from the ordinary and dark muscle myosins of mackerel Pneumatophorus japonicus japonicus. Ordinary muscle myosin light chains were isolated from each other by DEAE-cellulose column chromatography using a linear gradient in potassium phosphate buffer (pH 6.0), whereas dark muscle myosin light chains, by the same chromatography, but in the presence of 4M urea. Five light chains thus isolated were analyzed for molecular weight and isoelectric point. The ordinary muscle myosin contained two moles of DTNB light chain per mole and another two moles of alkali light chains A1 and A2. The molar ratio of A1 to A2 was about 0.4. The molecular weights of A1 (27, 000) and A2 (21, 000) were larger than that of DTNB light chain (19, 000). The dark muscle myosin contained two moles each of two light chains, D1 and D2, whose molecular weights were 24, 500 and 20, 000, respectively. The isoelectric points of A1, A2 and DTNB light chains were 4.9, 4.4, and 4.8, respectively, while those of D1 and D2 light chains were 5.6 and 5.1, respectively.