Acetylation at the N-terminus of actin strengthens weak interaction between actin and myosin

The N-terminus of all actins so far studied is acetylated. Although the pat hways of acetylation have been well studied, its functional importance has been unclear. A negative charge cluster in the actin N-terminal region is s hown to be important for the function of actomyosin. Acetylation at the N-t erminus removes a positive charge and increases the amount of net negative charges in the N-terminal region. This may augment the role of the negative charge cluster. To examine this possibility, actin with a nonacetylated N- terminus (nonacetylated actin) was produced. The nonacetylated actin polyme rized and depolymerized normally. In actin-activated heavy meromyosin ATPas e assays, the nonacetylated actin showed higher K-app without significantly changing V-max, compared with those of wild-type actin, This is in contras t to the effect of the N-terminal negative charge cluster, which increases V-max without changing K-app. These results indicate that the acetylation a t the N-terminus of actin strengthens weak actomyosin interaction. (C) 2000 Academic Press.