Plant villin, lily P-135-ABP, possesses G-actin binding activity and accelerates the polymerization and depolymerization of actin in a Ca2+-sensitive manner.
Plant villin, lily P-135-ABP, possesses G-actin binding activity and accelerates the polymerization and depolymerization of actin in a Ca2+-sensitive manner.
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DOI：
10.1093/pcp/pci185
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发表时间：
2005-10
影响因子：
4.9
通讯作者：
E. Yokota;M. Tominaga;I. Mabuchi;Yasunori Tsuji;C. Staiger;K. Oiwa;T. Shimmen
中科院分区：
文献类型：
--
作者：
E. Yokota;M. Tominaga;I. Mabuchi;Yasunori Tsuji;C. Staiger;K. Oiwa;T. Shimmen
从百合的发芽花粉中，已通过生化方法鉴定出了两种类型的绒毛蛋白：P-115-ABP 和 P-135-ABP。先前已证明两种绒毛具有 Ca(2+)-CaM 依赖性肌动蛋白丝结合和成束活性。在这里，我们研究了百合绒毛对肌动蛋白聚合和解聚的影响。 P-115-ABP 和 P-135-ABP 存在于从发芽花粉中制备的粗蛋白提取物中，该粗蛋白提取物以 Ca(2+) 依赖性方式与 DNase I 亲和柱结合。纯化的 P-135-ABP 缩短了在 Ca(2+) 或 Ca(2+)-CaM 存在下单体肌动蛋白丝聚合之前的滞后期。这些结果表明，在Ca(2+)存在下，P-135-ABP可以与G-肌动蛋白形成复合物，并且该复合物充当肌动蛋白丝聚合的核。然而，P-135-ABP 的成核活性可能与体内无关，因为用 profilin 饱和的 G-肌动蛋白的组装（模拟花粉中的条件）在 P-135-ABP 存在的情况下并未加速。 P-135-ABP 还增强了稀释介导的分解过程中肌动蛋白丝的解聚。在 Ca(2+)-CaM 存在下，细丝倒刺末端的生长也被阻止，这与细丝封盖活性一致。这些结果表明，百合绒毛不仅参与花粉管基部和柄区域肌动蛋白丝排列成束，而且还通过其在花粉管顶端区域Ca(2+)浓度相对较高的加帽和解聚（或断裂）活性来调节和调节肌动蛋白动力学。
From germinating pollen of lily, two types of villins, P-115-ABP and P-135-ABP, have been identified biochemically. Ca(2+)-CaM-dependent actin-filament binding and bundling activities have been demonstrated for both villins previously. Here, we examined the effects of lily villins on the polymerization and depolymerization of actin. P-115-ABP and P-135-ABP present in a crude protein extract prepared from germinating pollen bound to a DNase I affinity column in a Ca(2+)-dependent manner. Purified P-135-ABP reduced the lag period that precedes actin filament polymerization from monomers in the presence of either Ca(2+) or Ca(2+)-CaM. These results indicated that P-135-ABP can form a complex with G-actin in the presence of Ca(2+) and this complex acts as a nucleus for polymerization of actin filaments. However, the nucleation activity of P-135-ABP is probably not relevant in vivo because the assembly of G-actin saturated with profilin, a situation that mimics conditions found in pollen, was not accelerated in the presence of P-135-ABP. P-135-ABP also enhanced the depolymerization of actin filaments during dilution-mediated disassembly. Growth from filament barbed ends in the presence of Ca(2+)-CaM was also prevented, consistent with filament capping activity. These results suggested that lily villin is involved not only in the arrangement of actin filaments into bundles in the basal and shank region of the pollen tube, but also in regulating and modulating actin dynamics through its capping and depolymerization (or fragmentation) activities in the apical region of the pollen tube, where there is a relatively high concentration of Ca(2+).