Song H, Endow S A
Department of Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Nature. 1998 Dec 10;396(6711):587-90. doi: 10.1038/25153.
Molecular motors require ATP to move along microtubules or actin filaments. To understand how molecular motors function, it is crucial to know how binding of the motor to its filamentous track stimulates the hydrolysis of ATP by the motor, enabling it to move along the filament. A mechanism for the enhanced ATP hydrolysis has not been elucidated, but it is generally accepted that conformational changes in the motor proteins occur when they bind to microtubules or actin filaments, facilitating the release of ADP. Here we report that a mutation in the motor domain of the microtubule motor proteins Kar3 and Ncd uncouples nucleotide- and microtubule-binding by the proteins, preventing activation of the motor ATPase by microtubules. Unlike the wild-type motors, the mutants bind tightly to both ADP and microtubules, indicating that interactions between the nucleotide- and microtubule-binding sites are blocked. The region of the motor that includes the mutated amino acid could transmit or undergo a conformational change required to convert the motor ATPase into a microtubule-stimulated state.
分子马达需要ATP才能沿着微管或肌动蛋白丝移动。为了理解分子马达的功能，关键是要知道马达与其丝状轨道的结合如何刺激马达水解ATP，使其能够沿着细丝移动。增强ATP水解的机制尚未阐明，但人们普遍认为，当马达蛋白与微管或肌动蛋白丝结合时，会发生构象变化，从而促进ADP的释放。在这里，我们报告微管马达蛋白Kar3和Ncd的马达结构域中的一个突变使蛋白质的核苷酸结合和微管结合解偶联，从而阻止微管激活马达ATP酶。与野生型马达不同，突变体与ADP和微管都紧密结合，这表明核苷酸结合位点和微管结合位点之间的相互作用被阻断。包含突变氨基酸的马达区域可能传递或经历将马达ATP酶转化为微管刺激状态所需的构象变化。
