Gambin Y, Lopez-Esparza R, Reffay M, Sierecki E, Gov N S, Genest M, Hodges R S, Urbach W
Laboratoire de Physique Statistique de l'Ecole Normale Supérieure, Unité Mixte de Recherche 8550, Centre National de la Recherche Scientifique-Université Paris 6, 24 Rue Lhomond, 75005 Paris, France.
Proc Natl Acad Sci U S A. 2006 Feb 14;103(7):2098-102. doi: 10.1073/pnas.0511026103. Epub 2006 Feb 6.
The biological function of transmembrane proteins is closely related to their insertion, which has most often been studied through their lateral mobility. For >30 years, it has been thought that hardly any information on the size of the diffusing object can be extracted from such experiments. Indeed, the hydrodynamic model developed by Saffman and Delbrück predicts a weak, logarithmic dependence of the diffusion coefficient D with the radius R of the protein. Despite widespread use, its validity has never been thoroughly investigated. To check this model, we measured the diffusion coefficients of various peptides and transmembrane proteins, incorporated into giant unilamellar vesicles of 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC) or in model bilayers of tunable thickness. We show in this work that, for several integral proteins spanning a large range of sizes, the diffusion coefficient is strongly linked to the protein dimensions. A heuristic model results in a Stokes-like expression for D, (D proportional, variant 1/R), which fits literature data as well as ours. Diffusion measurement is then a fast and fruitful method; it allows determining the oligomerization degree of proteins or studying lipid-protein and protein-protein interactions within bilayers.
跨膜蛋白的生物学功能与其插入密切相关，而这一点通常是通过其侧向移动性来研究的。三十多年来，人们一直认为，从这类实验中几乎无法获取有关扩散物体大小的任何信息。实际上，萨夫曼和德尔布吕克提出的流体动力学模型预测，扩散系数D与蛋白质半径R之间存在微弱的对数依赖关系。尽管该模型被广泛应用，但其有效性从未得到彻底研究。为了检验这个模型，我们测量了多种肽和跨膜蛋白的扩散系数，这些肽和蛋白被整合到1-硬脂酰-2-油酰-sn-甘油-3-磷酸胆碱（SOPC）的巨型单层囊泡中，或处于可调厚度的模型双层膜中。我们在这项工作中表明，对于几种大小范围广泛的整合蛋白，扩散系数与蛋白质尺寸密切相关。一个启发式模型得出了一个类似于类似类似于斯托克斯型的D表达式（D与1/R成正比），它与文献数据以及我们的数据都拟合得很好。因此，扩散测量是一种快速且有效的方法；它能够确定蛋白质的寡聚化程度，或研究双层膜内的脂-蛋白和蛋白-蛋白相互作用。
