[Limited trypsinolysis of alpha-actin and the distribution of sulfhydryl groups in the molecular fragments].

Incubation of alpha-actinin with trypsin leads to the formation of several fragments with molecular weight of 55 000, 38 000, 30 000 and 15 000 which are rather resistant against further proteinase action. Two from five exposed cysteine residues modified by N-ethylmaleimide in the polypeptide chain of the subunit are located in the 55 000 fragment, one in the 30 000 fragment, and the remaining two appear to belong to those parts of the polypeptide chain that are subject to degradation to small peptides under the action of trypsin. Masked SH-groups are localized to the 30 000 fragment.