[Sulfhydryl groups of alpha-actinin]

It has been established that the molecule of alpha-actinin (m. w. 200 000) contains 16 SH-groups, which are distinguished by their activity. Six SH-groups may be comparatively easily discovered in the native protein. Four partly "masked" SH-groups are titrated in the low acidic media. Five-six SH-groups are completely masked and are revealed only after denaturation of protein. Blocking of SH-groups of alpha-actinin by the parachloromercuribenzoate decreases the biological activity of alpha-actinin measured by the formation of the alpha-actinin--actin complex. It has been shown that partly "masked" SH-groups revealed with the temperature increase are not incorporated into the active centre and do not take part in protein functioning.