Affinity chromatography of heavy meromyosin subfragment-1 reacted with thiol reagents.

Separation of heavy meromyosin subfragment-1 treated with N-ethyl maleimide (MalNEt) into native -SH1- and -(SH1, SH2)-blocked protein populations could be achieved by affinity chromatography on agarose-ATP columns in the presence of Mg2+ or Ca2+. Covalent bridging of the two -SH groups by p-phenylenedimaleimide gave a product which has the same affinity of binding to ATP columns as the doubly blocked MalNEt preparation. Treatment with p-phenylenedimaleimide abolished binding to immobilized F-actin columns, whereas modifications by MalNEt did not affect adsorption by this chromatographic medium. Affinity chromatography on immobilized nucleotide and actin columns is suggested as an analytical tool in the study of the involvement of thiol groups in the myosin active site and its conformation.