Abe A, Saeki K, Yasunaga T, Wakabayashi T
Department of Physics, School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-0033, Japan.
Biochem Biophys Res Commun. 2000 Feb 5;268(1):14-9. doi: 10.1006/bbrc.1999.2069.
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 K(app) without significantly changing V(max), compared with those of wild-type actin. This is in contrast to the effect of the N-terminal negative charge cluster, which increases V(max) without changing K(app). These results indicate that the acetylation at the N-terminus of actin strengthens weak actomyosin interaction.
到目前为止，所有已研究的肌动蛋白的N端均被乙酰化。虽然乙酰化途径已得到充分研究，但其功能重要性尚不清楚。肌动蛋白N端区域的一个负电荷簇对肌动球蛋白的功能很重要。N端的乙酰化去除了一个正电荷，增加了N端区域的净负电荷数量。这可能增强了负电荷簇的作用。为了检验这种可能性，制备了具有非乙酰化N端的肌动蛋白（非乙酰化肌动蛋白）。非乙酰化肌动蛋白的聚合和解聚正常。在肌动蛋白激活的重酶解肌球蛋白ATP酶分析中，与野生型肌动蛋白相比，非乙酰化肌动蛋白显示出更高的表观解离常数（K(app)），而最大反应速度（V(max)）没有显著变化。这与N端负电荷簇的作用相反，负电荷簇增加V(max)而不改变K(app)。这些结果表明，肌动蛋白N端的乙酰化增强了弱的肌动球蛋白相互作用。
