POST-TRANSLATIONAL MODIFICATION OF ACTINS SYNTHESIZED INVITRO

It has been shown in two different ways that β and γ actins synthesized in vitro are acetylated and that the minor species of actin, δ and ε{lunate}, are non-acetylated forms of β and γ actin, respectively. Firstly, addition of acetyl-CoA to the wheat germ system translating poly(A)-containing RNA from unfused rat L6 myoblasts, resulted in an increase in the synthesis of β and γ actins at the expense of δ and ε{lunate} actins. Secondly, β and γ actins were labeled when synthesized in vitro in the presence of [3H]acetyl-CoA. No label was detectable in δ and ε{lunate} actins. By extrapolation this indicates that β and γ actin are acetylated in vivo, probably at the N-terminus. β and γ actins synthesized in vivo contain a Nγ-methylhistidine residue, but no methylation of β and γ actins synthesized in vitro was detectable, using S-[3H]adenosylmethionine as a methyl donor. © 1979.