Vuillard L, Roux B, Miller A
Department of Biochemistry, University of Edinburgh Medical School, Scotland.
Eur J Biochem. 1990 Jul 31;191(2):333-6. doi: 10.1111/j.1432-1033.1990.tb19127.x.
Although the conformation of fibronectin has been widely investigated by various techniques, there has not yet been any determination of its rotational diffusion coefficient. We report here this determination by the transient electric birefringence study of solutions of bovine plasma fibronectin at physiological ionic strength. The solutions showed a positive birefringence. A linear relationship was observed between the intensity of the birefringence at equilibrium and the square of the electric field within the range of fields applied (up to 12.5 kV.cm-1). The field-independent decay of the induced birefringence was described by a single exponential with a relaxation time of 0.76 (+/- 0.08) microsecond at 23 degrees C. This establishes fibronectin in solution as a globally rigid structure with a rotational diffusion coefficient, at 20 degrees C, of 202,000 s-1. This result allows the first rigorous determination of the low-resolution structure of fibronectin. It is important to notice that the analysis combines only results obtained in physiological conditions on native molecules and follows a strict hydrodynamic interpretation. The conclusion of this work is that a hollow sphere of about 20 nm external diameter can be proposed as a model for the three-dimensional structure of the fibronectin molecule in solution. This new model suggests the fibronectin could have the structure of a carrier protein.
尽管已经通过各种技术对纤连蛋白的构象进行了广泛研究，但尚未对其旋转扩散系数进行任何测定。我们在此报告通过对生理离子强度下牛血浆纤连蛋白溶液进行瞬态电双折射研究来测定该系数。这些溶液呈现出正双折射。在所施加电场范围（高达12.5 kV·cm⁻¹）内，观察到平衡时双折射强度与电场平方之间呈线性关系。诱导双折射的场强无关衰减由一个单指数描述，在23℃时弛豫时间为0.76（±0.08）微秒。这表明溶液中的纤连蛋白是一种整体刚性结构，在20℃时旋转扩散系数为202,000 s⁻¹。该结果使得首次能够严格确定纤连蛋白的低分辨率结构。重要的是要注意，该分析仅结合了在生理条件下对天然分子获得的结果，并遵循严格的流体动力学解释。这项工作的结论是，可以提出一个外径约20 nm的空心球体作为溶液中纤连蛋白分子三维结构的模型。这个新模型表明纤连蛋白可能具有载体蛋白的结构。
