Toya M, Motegi F, Nakano K, Mabuchi I, Yamamoto M
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
Genes Cells. 2001 Mar;6(3):187-99. doi: 10.1046/j.1365-2443.2001.00414.x.
Type I myosin is highly conserved among eukaryotes, and apparently plays important roles in a number of cellular processes. In the budding yeast, two myosin I species have been identified and their role in F-actin assembly has been inferred.
We cloned the fission yeast myo1 gene, which apparently encoded a myosin I protein. Disruption of myo1 was not lethal, but it caused growth retardation at high and low temperatures, sensitivity to a high concentration of KCl, and aberrance in cell morphology associated with an abnormal distribution of F-actin patches. An abnormal deposition of cell wall materials was also seen. Homothallic myo1Delta cells could mate, but heterothallic myo1Delta cells were poor in conjugation. Myo1p was necessary for the encapsulation of spores. The tail domain of Myo1p was pivotal for its function. Calmodulin could bind to Myo1p through the IQ domain at the neck.
Myo1p appears to control the redistribution of F-actin patches during the cell cycle. Loss of Myo1p function is likely to slow down the actin assembly/disassembly process, which results in a failure of the actin cycle to catch up with other events in both the mitotic and meiotic cell cycles, including extension of the conjugation tubes.
I型肌球蛋白在真核生物中高度保守，显然在许多细胞过程中发挥重要作用。在芽殖酵母中，已鉴定出两种肌球蛋白I，并推断出它们在F-肌动蛋白组装中的作用。
我们克隆了裂殖酵母的myo1基因，该基因显然编码一种肌球蛋白I蛋白。破坏myo1并不致命，但会导致在高温和低温下生长迟缓、对高浓度KCl敏感以及与F-肌动蛋白斑块异常分布相关的细胞形态异常。还观察到细胞壁物质的异常沉积。同宗配合的myo1Δ细胞可以交配，但异宗配合的myo1Δ细胞在接合方面表现不佳。Myo1p是孢子包被所必需的。Myo1p的尾部结构域对其功能至关重要。钙调蛋白可以通过颈部的IQ结构域与Myo1p结合。
Myo1p似乎在细胞周期中控制F-肌动蛋白斑块的重新分布。Myo1p功能的丧失可能会减缓肌动蛋白组装/拆卸过程，这导致肌动蛋白循环无法跟上有丝分裂和减数分裂细胞周期中的其他事件，包括接合管的延长。
