Posttranslational Processing of Brain Actin

Two short‐lived isoforms of actin, named δ‐ and ε‐actin, have been detected in brain extracts from rats labeled in vivo with [35S]methionine. These two molecular species have PI values slightly more basic than β‐ and γ‐actin, the stable isoforms of the protein found in brain tissue. Under the appropriate incubation conditions δ‐ and ε‐actin, synthesized in vivo, can be converted in vitro into β‐ and γ‐actin. This posttranslational processing of δ‐ and ε‐actin requires acetyl coenzyme A, suggesting that an acetylation step, presumably of the NH2‐terminal end, is involved in the transformation of these proteins into β‐ and γ‐actin.