Acetylation at the N-Terminus of Actin Strengthens Weak Interaction between Actin and Myosin

Abstract

The N-terminus of all actins so far studied is acetylated. Although the pathways of acetylation have been well studied, its functional importance has been unclear. A negative charge cluster in the actin N-terminal region is shown to be important for the function of actomyosin. Acetylation at the N-terminus 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 polymerized and depolymerized normally. In actin-activated heavy meromyosin ATPase assays, the nonacetylated actin showed higher Kapp without significantly changing Vmax, compared with those of wild-type actin. This is in contrast to the effect of the N-terminal negative charge cluster, which increases Vmax without changing Kapp. These results indicate that the acetylation at the N-terminus of actin strengthens weak actomyosin interaction.