Fig.5. Electrophoretic separation and western blot analysis of I. emarginata myosin, actomyosin and thin filament on 15% SDS gels. The positions of molecular mass standards (kDa) are indicated. (A) In the myosin extract three myosin light chains (myosin LC) were identified (asterisks). In myosin LC extracts obtained by guanidine–HCl precipitation two of these light chains (14kDa and 18.5kDa) are present. (B) The actomyosin and thin filament extracts contain a protein with the apparent molecular mass of 30kDa (arrow), whereas no such protein is present in the myosin extract. (C) Western blot analysis with a phosphoserine antibody reveals a number of high molecular mass proteins and two proteins at 30kDa and 31kDa in thin filament preparations. (D) In I. emarginata muscle homogenates and thin filament preparations, a major band at 30kDa (arrow) and a minor band at 31kDa are stained in western blot analysis with antiserum against lobster troponin I₃.