Modulation of actin structure and function by phosphorylation of Tyr-53 and profilin binding
Modulation of actin structure and function by phosphorylation of Tyr-53 and profilin binding
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DOI：
10.1073/pnas.0805852105
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发表时间：
2008-08-19
影响因子：
11.1
通讯作者：
Dominguez, Roberto
中科院分区：
文献类型：
--
作者：
Baek, Kyuwon;Liu, Xiong;Dominguez, Roberto
在饥饿时，网囊藻细胞聚集形成含有孢子的多细胞子实体，当转移到营养丰富的培养基时，孢子萌发。这种发育周期与酪氨酸-53（pY 53-actin）处的肌动蛋白磷酸化程度相关，其在营养细胞中低，但在活的成熟孢子中高。在这里，我们描述了高分辨率的晶体结构的pY 53-肌动蛋白和未磷酸化的肌动蛋白与凝溶胶蛋白片段1和profilin的复合物。在pY 53-actin的结构中，Tyr-53上的磷酸基团与肌动蛋白的DNA酶1结合环（D-环）的残基进行氢键相互作用，导致D-环的构象比未磷酸化的结构更稳定。一个更严格折叠的D环可以解释一些先前描述的性质pY 53-actin，包括其增加的聚合临界浓度，降低成核率和尖端延伸，和弱的亲和力DNA酶I。我们在这里表明，酪氨酸-53磷酸化抑制枯草杆菌蛋白酶切割的ID-环，并降低肌动蛋白上的核苷酸交换率。profilin-Dictyosteoblast-actin的结构与先前确定的profilin-beta-actin和profilin-alpha-actin的结构惊人地相似。通过比较这组具有代表性的profilin-actin结构与其他结构的肌动蛋白，我们强调profilin的肌动蛋白构象的影响。在profilin-actin复合物中，肌动蛋白的亚结构域1和3围绕profilin闭合，产生肌动蛋白的两个主要结构域相对于彼此的4.7度旋转。因此，核苷酸裂缝变得更加适度开放的profilin-actin复合物，可能解释的刺激核苷酸交换肌动蛋白profilin。
On starvation, Dictyostelium cells aggregate to form multicellular fruiting bodies containing spores that germinate when transferred to nutrient-rich medium. This developmental cycle correlates with the extent of actin phosphorylation at Tyr-53 (pY53-actin), which is low in vegetative cells but high in viable mature spores. Here we describe high-resolution crystal structures of pY53-actin and unphosphorylated actin in complexes with gelsolin segment 1 and profilin. In the structure of pY53-actin, the phosphate group on Tyr-53 makes hydrogen-bonding interactions with residues of the DNase 1-binding loop (D-loop) of actin, resulting in a more stable conformation of the D-loop than in the unphosphorylated structures. A more rigidly folded D-loop may explain some of the previously described properties of pY53-actin, including its increased critical concentration for polymerization, reduced rates of nucleation and pointed end elongation, and weak affinity for DNase I. We show here that phosphorylation of Tyr-53 inhibits subtilisin cleavage of the ID-loop and reduces the rate of nucleotide exchange on actin. The structure of profilin-Dictyostelium-actin is strikingly similar to previously determined structures of profilin-beta-actin and profilin-alpha-actin. By comparing this representative set of profilin-actin structures with other structures of actin, we highlight the effects of profilin on the actin conformation. In the profilin-actin complexes, subdomains 1 and 3 of actin close around profilin, producing a 4.7 degrees rotation of the two major domains of actin relative to each other. As a result, the nucleotide cleft becomes moderately more open in the profilin-actin complex, probably explaining the stimulation of nucleotide exchange on actin by profilin.