Fujiwara S, Kull F J, Sablin E P, Stone D B, Mendelson R A
Cardiovascular Research Institute, University of California, San Francisco 94143, USA.
Biophys J. 1995 Oct;69(4):1563-8. doi: 10.1016/S0006-3495(95)80028-7.
The shapes of the motor domains of kinesin and ncd, which move in opposite directions along microtubules, have been investigated. Using proteins expressed in Escherichia coli, it was found that at high salt (> 200 mM) Drosophila ncd motor domain (R335-K700) and human kinesin motor domain (M1-E349) were both sufficiently monomeric to allow an accurate determination of their radii of gyration (Rg) and their molecular weights. The measured Rg values of the ncd and kinesin motor domains in D2O were 2.06 +/- 0.06 and 2.05 +/- 0.04 nm, respectively, and the molecular weights were consistent with those computed from the amino acid compositions. Fitting of the scattering curves to approximately 3.5 nm resolution showed that the ncd and kinesin motor domains can be described adequately by triaxial ellipsoids having half-axes of 1.42 +/- 0.38, 2.24 +/- 0.44, and 3.65 +/- 0.22 nm, and half-axes of 1.52 +/- 0.23, 2.00 +/- 0.25, and 3.73 +/- 0.10 nm, respectively. Both motor domains are described adequately as somewhat flattened prolate ellipsoids with a maximum dimension of approximately 7.5 nm. Thus, it appears that the overall shapes of these motor domains are not the major determinants of the directionality of their movement along microtubules.
已经对驱动蛋白和Ncd的运动结构域的形状进行了研究，它们沿微管向相反方向移动。利用在大肠杆菌中表达的蛋白质，发现在高盐（>200 mM）条件下，果蝇Ncd运动结构域（R335-K700）和人驱动蛋白运动结构域（M1-E349）都足够单体化，以允许准确测定其回转半径（Rg）和分子量。在重水中测得的Ncd和驱动蛋白运动结构域的Rg值分别为2.06±0.06和2.05±0.04 nm，分子量与根据氨基酸组成计算的值一致。将散射曲线拟合到约3.5 nm分辨率表明，Ncd和驱动蛋白运动结构域可以用三轴椭球体充分描述，其半轴分别为1.42±0.38、2.24±0.44和3.65±0.22 nm，以及1.52±0.23、2.00±0.25和3.73±0.10 nm。两个运动结构域都被充分描述为有点扁平的长椭球体，最大尺寸约为7.5 nm。因此，这些运动结构域的整体形状似乎不是其沿微管运动方向性的主要决定因素。
