RESUMO
It had previously been reported (B. Krzysik, J. P. Vergnes, and I. R. McManus (1971) Arch. Biochem. Biophys. 146, 34-45) that prior to day 11 of embryonic life chick skeletal muscle actin contained little or no 3-methylhistidine, and that between Day 11 and 18, the degree of actin histidine methylation increased until it leveled off at 1 mol of 3-methylhistidine/mol actin. This is the value seen in adult muscle and nonmuscle actins so far analyzed. To determine whether this delayed onset of actin methylation occurred simultaneously throughout the organism or differed from tissue to tissue, the 3-methylhistidine content of cardiac muscle actin from Day 2 of embryonic life to hatching and of brain actin at Days 9, 11, and 14 were analyzed. These results, obtained by analyzing unlabeled actin samples as well as samples labeled in vivo with [3H]histidine, showed that at all stages, 1 mol of 3-methylhistidine was present per mol of actin. When skeletal muscle samples obtained from Day 11 to 18 embryos were analyzed 1 mol of 3-methylhistidine/mol of actin was observed. Thus, in the chick embryo, contrary to those reports published earlier, it was found that actin histidine methylation is not under developmental control.
