CONTINUATION OF SYMPOSIUM: FUNDAMENTAL PROPERTIES OF MUSCLE PROTEINS IMPORTANT IN MEAT SCIENCE: ROLE OF NEW CYTOSKELETAL ELEMENTS IN MAINTENANCE OF MUSCLE INTEGRITY

Evidence suggests that desmin, titin and nebulin, three recently discovered proteins, have cytoskeletal roles in muscle cells. The three proteins have been purified from mature skeletal muscle and partially characterized. Properties of the three proteins are described, with special regard to their probable roles and importance in maintaining muscle cell integrity. Results will be shown that demonstrate ability of purified desmin to self-assemble into synthetic 10-nm (intermediate) diameter filaments. Taken together with immunoelectron microscope results (Richardson et al. 1981), it is evident that desmin is the major component of 10-nm filaments of mature skeletal muscle cells and that the desmin filaments link adjacent myofibrils at their Z-line levels and seemingly tie the myofibrils into the cell cyto-skeleton. Desmin is degraded at about the same rate as is the highly susceptible troponin-T in bovine semitendinosus muscle postmortem. Alterations in desmin and other recently discovered cytoskeletal proteins would be expected to disrupt muscle cell integrity and to have marked effects on properties of muscle important to its use as food.