Hydrolysis of ATP and reversible binding to F-actin by myosin heavy chains free of all light chains

Abstract

Myosin has two ‘heads’ or subfragments-1 (S-1) each containing a heavy chain, a phosphorylatable or ‘regulatory’ light chain and another light chain which is generally referred to as being essential^1–3. The regulatory light chains can be removed without loss of ATPase activity³, but until now it has not been possible to remove the other class of light chain without complete loss of ATPase activity⁴. However, the dissociating conditions used also denature the heavy chains, and inactivation frequently precedes light-chain dissociation⁵. We now describe the use of mild dissociating conditions combined with affinity chromatography using antibodies to the alkali light chains to produce light-chain-free S-1 heavy chains. The S-1 heavy chain binds reversibly to F-actin and has 30–80% of the ATPase activities of native S-1.