Perkins S J, Sim R B
Eur J Biochem. 1986 May 15;157(1):155-68. doi: 10.1111/j.1432-1033.1986.tb09652.x.
Solution scattering experiments using both X-rays and neutrons are reported for human complement component C3 and up to six other glycoprotein fragments that are derived from C3. The X-ray and neutron molecular masses and neutron matchpoints are in agreement with the known primary sequence of C3. The X-ray radius of gyration RG of C3 is 5.2 nm and is similar for the related forms C3u, C3(a + b) and C3b. The X-ray cross-sectional radius of gyration RXS of C3b is however less than that of C3, C3u and C3(a + b). The major fragments of C3b, namely C3c and C3dg, were studied. The RG of C3c is 4.7 nm and for C3dg is 2.9 nm. C3c and C3dg do not interact when they coexist in solution in equimolar amounts. When C3u is cleaved into iC3u, the RG of iC3u increases to 5.9 nm and its RXS decreases, showing that C3c and C3dg behave as independent entities within the parent glycoprotein. Analyses of the neutron RG and RXS values by contrast variation techniques confirm the X-ray analyses, and show no evidence for significant hydrophobic or hydrophilic domains within C3 or any of its fragments. Shape analyses show that C3, C3c and C3dg are elongated particles. Debye models were developed using the scattering curve out to Q = 1.6 nm-1. These show that C3 and C3c resemble oblate ellipsoids while C3dg resembles a prolate ellipsoid. C3dg lies on the long edge of C3c within C3. The dimensions of the models are 18 nm X 2 nm X 10 nm for C3, 18 nm X 2 nm X 7 nm for C3c and 10 nm X 2 nm X 3 nm for C3dg. These models are compatible with analyses of the scattering curve RG and RXS values, data from sedimentation coefficients, and images of C3 and C3c seen by electron microscopy.
报告了使用X射线和中子对人补体成分C3以及多达六个源自C3的其他糖蛋白片段进行的溶液散射实验。X射线和中子分子质量以及中子匹配点与已知的C3一级序列一致。C3的X射线回转半径RG为5.2 nm，对于相关形式的C3u、C3(a + b)和C3b来说相似。然而，C3b的X射线截面回转半径RXS小于C3、C3u和C3(a + b)的。研究了C3b的主要片段，即C3c和C3dg。C3c的RG为4.7 nm，C3dg的为2.9 nm。当C3c和C3dg以等摩尔量共存于溶液中时它们不相互作用。当C3u裂解为iC3u时，iC3u的RG增加到5.9 nm且其RXS减小，表明C3c和C3dg在母体糖蛋白内表现为独立实体。通过对比变化技术对中子RG和RXS值的分析证实了X射线分析，并且未显示C3或其任何片段内存在显著疏水或亲水域的证据。形状分析表明C3、C3c和C3dg是细长颗粒。使用散射曲线直至Q = 1.6 nm-1建立了德拜模型。这些表明C3和C3c类似于扁椭球体，而C3dg类似于长椭球体。C3dg位于C3内C3c的长边上。C3的模型尺寸为18 nm×2 nm×10 nm，C3c的为18 nm×2 nm×7 nm，C3dg的为10 nm×2 nm×3 nm。这些模型与散射曲线RG和RXS值的分析、沉降系数数据以及电子显微镜下看到的C3和C3c图像兼容。
