Lister Ida, Schmitz Stephan, Walker Matthew, Trinick John, Buss Folma, Veigel Claudia, Kendrick-Jones John
MRC Laboratory of Molecular Biology, Hills Road, Cambridge, UK.
EMBO J. 2004 Apr 21;23(8):1729-38. doi: 10.1038/sj.emboj.7600180. Epub 2004 Mar 25.
Myosin VI is involved in a wide variety of intracellular processes such as endocytosis, secretion and cell migration. Unlike almost all other myosins so far studied, it moves towards the minus end of actin filaments and is therefore likely to have unique cellular properties. However, its mechanism of force production and movement is not understood. Under our experimental conditions, both expressed full-length and native myosin VI are monomeric. Electron microscopy using negative staining revealed that the addition of ATP induces a large conformational change in the neck/tail region of the expressed molecule. Using an optical tweezers-based force transducer we found that expressed myosin VI is nonprocessive and produces a large working stroke of 18 nm. Since the neck region of myosin VI is short (it contains only a single IQ motif), it is difficult to reconcile the 18 nm working stroke with the classical 'lever arm mechanism', unless other structures in the molecule contribute to the effective lever. A possible model to explain the large working stroke of myosin VI is presented.
肌球蛋白VI参与多种细胞内过程，如内吞作用、分泌和细胞迁移。与目前研究的几乎所有其他肌球蛋白不同，它向肌动蛋白丝的负极移动，因此可能具有独特的细胞特性。然而，其产生力和运动的机制尚不清楚。在我们的实验条件下，表达的全长肌球蛋白VI和天然肌球蛋白VI均为单体。使用负染色的电子显微镜显示，ATP的添加会在表达分子的颈部/尾部区域诱导大的构象变化。使用基于光镊的力传感器，我们发现表达的肌球蛋白VI是非连续性的，并且产生18 nm的大工作行程。由于肌球蛋白VI的颈部区域很短（仅包含一个IQ基序），除非分子中的其他结构有助于形成有效的杠杆臂，否则很难将18 nm的工作行程与经典的“杠杆臂机制”相协调。本文提出了一个解释肌球蛋白VI大工作行程的可能模型。
