Interaction of actin monomers with Acanthamoeba actophorin (ADF/cofilin) and profilin
Interaction of actin monomers with Acanthamoeba actophorin (ADF/cofilin) and profilin
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DOI：
10.1074/jbc.273.39.25106
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发表时间：
1998-09-25
影响因子：
4.8
通讯作者：
Pollard, TD
中科院分区：
文献类型：
--
作者：
Blanchoin, L;Pollard, TD
阿米巴actophorin是ADF/cofilin家族的成员，其结合肌动蛋白单体和细丝。我们用荧光各向异性研究肌动蛋白单体与重组肌动蛋白的相互作用，用罗丹明标记的半胱氨酸取代丝氨酸-88。标记的肌动蛋白保留其对肌动蛋白的亲和力和降低肌动蛋白丝的低剪切粘度的能力。在生理离子强度下，肌动蛋白结合Mg-ADP-肌动蛋白单体（Kd = 0.1 μ M）的强度比Mg-ATP-肌动蛋白单体强40倍。当结合到肌动蛋白单体，actophorin有没有影响的伸长在任何一端的肌动蛋白丝的Mg-ATP-肌动蛋白和略有增加的速率在两端的Mg-ADP-肌动蛋白。因此，actophorin不螯合肌动蛋白单体。沉降平衡超离心表明，actophorin和profilin竞争结合肌动蛋白单体。肌动蛋白和profilin对肌动蛋白单体结合的核苷酸交换速率有相反的作用。尽管肌动蛋白对ADP-肌动蛋白具有高亲和力，但生理浓度的profilin克服了肌动蛋白对ADP交换的抑制作用。Profilin迅速将ADP-肌动蛋白折叠回profilin-ATP-肌动蛋白池，为肌动蛋白丝的伸长做好准备。
Acanthamoeba actophorin is a member of ADF/cofilin family that binds both actin monomers and filaments. We used fluorescence anisotropy to study the interaction of actin monomers with recombinant actophorin labeled with rhodamine on a cysteine substituted for Serine-88. Labeled actophorin retains its affinity for actin and ability to reduce the low shear viscosity of actin filaments. At physiological ionic strength, actophorin binds Mg-ADP-actin monomers (K-d = 0.1 mu M) 40 times stronger than Mg-ATP-actin monomers. When bound to actin monomers, actophorin has no effect on elongation at either end of actin filaments by Mg-ATP-actin and slightly increases the rate of elongation at both ends by Mg-ADP-actin. Thus actophorin does not sequester actin monomers. Sedimentation equilibrium ultracentrifugation shows that actophorin and profilin compete for binding actin monomers. Actophorin and profilin have opposite effects on the rate of exchange of nucleotide bound to actin monomers. Despite the high affinity of actophorin for ADP-actin, physiological concentrations of profilin overcome the inhibition of ADP exchange by actophorin. Profilin rapidly recycles ADP-actin back to the profilin-ATP-actin pool ready for elongation of actin filaments.