Brain actin synthesized in vitro undergoes two different and sequential posttranslational modifications.

The have studied the posttranslational processing of actin molecules synthesized in a cell-free system. The results of these experiments indicate that during the in vitro synthesis of the actins from rat brain the primary translational products undergo two different and sequential posttranslational modifications. These modifications are accompanied by slight changes in the isoelectric points of the proteins and can be detected by isoelectric focusing analysis. The same posttranslational modifications can be detected during the in vitro synthesis of chick embryo skeletal muscle actin. The evidence presented suggest that the first posttranslational modification may correspond to the methylation of a histidine residue, and the second modification most likely corresponds to the acetylation of the NH(2)-terminal amino acid residues of actin molecules.