Heterogeneity of amino acid incorporation rate in adult skeletal muscle actin.

An actin preparation extracted at 25 degree C for 2 h from the residue which had previously been subjected to the routine extraction procedure, i.e. at 4 degree C for 15 min, showed markedly increased rates of amino acid incorporation, i.e. 48% higher than routinely extracted actin. The nature of the actin having higher amino acid incorporation rates was discussed in relation to 10S-actinin.