Paradies H H, Schmidt U D
J Biol Chem. 1979 Jun 25;254(12):5257-63.
The Mg2+- and Ca2+-stimulated ATPase (bacterial coupling factor) has been investigated in solution with different independent techniques. The molecular weight of the five-subunit enzyme was found to be 345,000 +/- 5,000 by means of light scattering, 350,000 by sedimentation equilibrium experiments, and 358,000 by means of small-angle x-ray scattering. The radius of gyration was found to be 41.9 A, the volume 7.39 x 10(5) A3, and the surface to volume ratio 5.5 x 10(-2) A-1 from small-angle x-ray scattering measurements of the enzyme in solution. The degree of hydration was found to be 0.62 ml of H2O/g of ATPase. The translational diffusion coefficient was determined to be 3.47 x 10(-7) cm2 s-1 by means of inelastic light scattering. The distribution of the scattered intensity near the origin appears to be bimodal, suggesting that the ATPase molecule is composed of spherical parts bound together by a flexible polypeptide chain. The largest dimension of the ATPase in solution is 120.0 A, determined from the pair distribution function.
已采用不同的独立技术对溶液中的镁离子和钙离子刺激的ATP酶（细菌偶联因子）进行了研究。通过光散射法测得五亚基酶的分子量为345,000±5,000，沉降平衡实验测得为350,000，小角X射线散射法测得为358,000。通过对溶液中该酶的小角X射线散射测量，回转半径为41.9 Å，体积为7.39×10⁵ ų，表面积与体积比为5.5×10⁻² Å⁻¹。测得水合程度为0.62 ml H₂O/g ATP酶。通过非弹性光散射法测定平移扩散系数为3.47×10⁻⁷ cm² s⁻¹。原点附近散射强度的分布似乎是双峰的，这表明ATP酶分子由通过柔性多肽链结合在一起的球形部分组成。根据对分布函数确定溶液中ATP酶的最大尺寸为120.0 Å。
