Molecular Characterization and Subcellular Localization of Arabidopsis Class VIII Myosin, ATM1
Molecular Characterization and Subcellular Localization of Arabidopsis Class VIII Myosin, ATM1
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DOI：
10.1074/jbc.m113.521716
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发表时间：
2014-05-02
影响因子：
4.8
通讯作者：
Ito, Kohji
中科院分区：
文献类型：
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作者：
Haraguchi, Takeshi;Tominaga, Motoki;Ito, Kohji
背景：VIII类肌球蛋白的分子特性还没有得到表征。结果：拟南芥第八类肌球蛋白，ATM 1，具有低的酶活性和高亲和力的肌动蛋白，主要定位于细胞皮层。结论：我们的数据表明，ATM 1作为一个张力传感器/发电机的功能。意义：这是第一次报道第八类肌球蛋白的酶和运动特性。陆地植物具有第八和第十一类肌球蛋白。虽然有一些关于XI类肌球蛋白的分子特性的信息，但VIII类肌球蛋白的特征还没有得到表征。在这里，我们报告的第一个分析的酶性质的第八类肌球蛋白。在杆状病毒系统中表达拟南芥VIII类肌球蛋白的马达结构域，ATM 1（ATM 1-MD），和马达结构域加一个IQ基序（ATM 1 - 1 IQ），并进行表征。ATM 1-MD和ATM 1 - 1 IQ对肌动蛋白的亲和力较高（K-actin = 4 m），但肌动蛋白激活的Mg ~（2+）-ATPase活性较低（V-max = 4 s（-1））。ATM 1-MD和ATM 1 - 1 IQ的肌动蛋白滑动速度分别为0.02和0.089 m/s，由此计算出全长ATM 1的值约为0.2 m/s。肌动蛋白共沉淀实验结果表明，ATM 1的占空比接近90%。ADP从肌动蛋白ATM 1复合物（acto-ATM 1）中解离非常缓慢，这是肌动蛋白滑动速度低、肌动蛋白激活的ATP酶活性低和占空比高的原因。ADP从acto-ATM 1上解离的速率明显呈双相性，即快相速率和慢相速率（分别为5.1和0.41 s（-1））。生理浓度的游离Mg 2+调节肌动蛋白滑动速度和肌动蛋白激活的ATP酶活性，通过改变ADP从acto-ATM 1解离的速率。拟南芥中表达的GFP融合全长ATM 1定位于胞间连丝、质体、新形成的细胞壁和细胞皮层的肌动蛋白丝。我们的研究结果表明，ATM 1功能作为一个张力传感器/发电机在细胞皮层和其他结构在拟南芥。
Background: Molecular properties of class VIII myosin are not characterized. Results:Arabidopsis class VIII myosin, ATM1, has low enzymatic activity and high affinity for actin and is primarily localized at the cell cortex. Conclusion: Our data suggest that ATM1 functions as a tension sensor/generator. Significance: This is the first report of enzymatic and motile properties of class VIII myosin.Land plants possess myosin classes VIII and XI. Although some information is available on the molecular properties of class XI myosins, class VIII myosins are not characterized. Here, we report the first analysis of the enzymatic properties of class VIII myosin. The motor domain of Arabidopsis class VIII myosin, ATM1 (ATM1-MD), and the motor domain plus one IQ motif (ATM1-1IQ) were expressed in a baculovirus system and characterized. ATM1-MD and ATM1-1IQ had low actin-activated Mg2+-ATPase activity (V-max = 4 s(-1)), although their affinities for actin were high (K-actin = 4 m). The actin-sliding velocities of ATM1-MD and ATM1-1IQ were 0.02 and 0.089 m/s, respectively, from which the value for full-length ATM1 is calculated to be approximate to 0.2 m/s. The results of actin co-sedimentation assay showed that the duty ratio of ATM1 was approximate to 90%. ADP dissociation from the actinATM1 complex (acto-ATM1) was extremely slow, which accounts for the low actin-sliding velocity, low actin-activated ATPase activity, and high duty ratio. The rate of ADP dissociation from acto-ATM1 was markedly biphasic with fast and slow phase rates (5.1 and 0.41 s(-1), respectively). Physiological concentrations of free Mg2+ modulated actin-sliding velocity and actin-activated ATPase activity by changing the rate of ADP dissociation from acto-ATM1. GFP-fused full-length ATM1 expressed in Arabidopsis was localized to plasmodesmata, plastids, newly formed cell walls, and actin filaments at the cell cortex. Our results suggest that ATM1 functions as a tension sensor/generator at the cell cortex and other structures in Arabidopsis.