Myosin 1G Is an Abundant Class I Myosin in Lymphocytes Whose Localization at the Plasma Membrane Depends on Its Ancient Divergent Pleckstrin Homology (PH) Domain (Myo1PH)
Myosin 1G Is an Abundant Class I Myosin in Lymphocytes Whose Localization at the Plasma Membrane Depends on Its Ancient Divergent Pleckstrin Homology (PH) Domain (Myo1PH)
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DOI：
10.1074/jbc.m109.086959
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发表时间：
2010-03-19
影响因子：
4.8
通讯作者：
Shaw, Stephen
中科院分区：
文献类型：
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作者：
Patino-Lopez, Genaro;Aravind, L.;Shaw, Stephen
I类肌球蛋白，连接F-肌动蛋白膜，在淋巴细胞中很大程度上是不确定的。淋巴细胞的质谱分析鉴定了两种短尾形式：（Myo 1G和Myo 1C）和一种长尾（Myo 1F）。我们研究了T淋巴细胞中最丰富的Myo 1G，并将关键发现与Myo 1C和Myo 1F进行了比较。Myo 1G定位于质膜，并以ATP可释放的方式与含肌动蛋白的不溶性颗粒结合。IQ +尾区的Myo 1G（Myo 1C和Myo 1F）是足够的膜定位，但膜定位增强的电机域。最小区域缺乏IQ基序，但包括：1）PH样结构域; 2）“Pre-PH”区域;和3）“Post-PH”区域。Pre-PH预测的α螺旋可能有助于静电，因为一个面上的两个保守的碱性残基是最佳膜定位所需的。我们的序列分析的特点不同的PH结构域家族，Myo 1 PH，也存在于长尾肌球蛋白，在真核蛋白无关的肌球蛋白，并在原核生物中的一个可能的祖先蛋白。Myo 1GMyo 1 PH结构域利用经典的脂质结合位点进行膜结合，因为突变“签名基序”中的两个碱性残基中的任一个都会破坏膜定位。Myo 1G Myo 1 PH结构域的每个碱性残基的突变揭示了β 3链中的另一个关键碱性残基，该残基仅由Myo 1D共享。Myo 1G与Myo 1C的不同之处在于其对膜结合的磷脂酰肌醇4，5-二磷酸依赖性，因为磷酸肌醇5-磷酸酶的膜定位从膜释放Myo 1C，而不是Myo 1G。因此，Myo 1 PH结构域可能在肌球蛋白I膜结合中发挥普遍作用，但不同亚型的结合特异性不同。
Class I myosins, which link F-actin to membrane, are largely undefined in lymphocytes. Mass spectrometric analysis of lymphocytes identified two short tail forms: (Myo1G and Myo1C) and one long tail (Myo1F). We investigated Myo1G, the most abundant in T-lymphocytes, and compared key findings with Myo1C and Myo1F. Myo1G localizes to the plasma membrane and associates in an ATP-releasable manner to the actin-containing insoluble pellet. The IQ + tail region of Myo1G (Myo1C and Myo1F) is sufficient for membrane localization, but membrane localization is augmented by the motor domain. The minimal region lacks IQ motifs but includes: 1) a PH-like domain; 2) a "Pre-PH" region; and 3) a "Post-PH" region. The Pre-PH predicted alpha helices may contribute electrostatically, because two conserved basic residues on one face are required for optimal membrane localization. Our sequence analysis characterizes the divergent PH domain family, Myo1PH, present also in long tail myosins, in eukaryotic proteins unrelated to myosins, and in a probable ancestral protein in prokaryotes. The Myo1GMyo1PH domain utilizes the classic lipid binding site for membrane association, because mutating either of two basic residues in the "signature motif" destroys membrane localization. Mutation of each basic residue of the Myo1G Myo1PH domain reveals another critical basic residue in the beta 3 strand, which is shared only by Myo1D. Myo1G differs from Myo1C in its phosphatidylinositol 4,5-bisphosphate dependence for membrane association, because membrane localization of phosphoinositide 5-phosphatase releases Myo1C from the membrane but not Myo1G. Thus Myo1PH domains likely play universal roles in myosin I membrane association, but different isoforms have diverged in their binding specificity.