Abstract
The preparation, structural and steady-state kinetic characteristics of contractile proteins from the leg muscle of frogs Rana temporaria and Rana pipiens are described. Actin and myosin from the two frog species are indistinguishable. The proteins have structural and steady-state kinetic properties similar to those from rabbit fast-twitch skeletal muscle. Chymotrypsin digestion of frog myosin or myofibrils in the presence of EDTA yields subfragment 1, which is separated by chromatography into two components that are distinguished by their alkali light-chain content.