Noncooperative Stabilization Effect of Phalloidin on ADP.BeFx- and ADP.AlF4-Actin Filaments

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• 作者：Jó ; zsef Orbá ; n ; Dé ; nes Lő ; rinczy ; Gá ; bor Hild ; Mikló ; s Nyitrai
• 刊名：Biochemistry
• 出版年：2008
• 出版时间：April 15, 2008
• 年：2008
• 卷：47
• 期：15
• 页码：4530 - 4534
• 全文大小：935K
• 年卷期：v.47,no.15(April 15, 2008)
• ISSN：1520-4995

文摘

Actin plays important roles in eukaryotic cell motility. During actin polymerization, the actin-bound ATP is hydrolyzed to ADP and P_i. We carried out differential scanning calorimetry experiments to characterize the cooperativity of the stabilizing effect of phalloidin on actin filaments in their ADP.P_i state. The ADP.P_i state was mimicked by using ADP.BeF_x or ADP.AlF₄. The results showed that the binding of the nucleotide analogues or phalloidin stabilized the actin filaments to a similar extent when added separately. Phalloidin binding to ADP.BeF_x- or ADP.AlF₄-actin filaments further stabilized them, indicating that the mechanism by which phalloidin and the nucleotide analogues affect the filament structure was different. The results also showed that the stabilization effect of phalloidin binding to ADP.BeF_x or ADP.AlF₄-bound actin filaments was not cooperative. Since the effect of phalloidin binding was cooperative in the absence of these nucleotide analogues, these results suggest that the binding of ADP.BeF_x or ADP.AlF₄ to the actin modified the protomer-protomer interactions along the actin filaments.