Influence of the Cosolute Environment on IgG Solution Structure Analyzed by Small-Angle X-ray Scattering
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- 作者：Wayne G. Lilyestrom ; Steven J. Shire ; Thomas M. Scherer
- 刊名：The Journal of Physical Chemistry B
- 出版年：2012
- 出版时间：August 16, 2012
- 年：2012
- 卷：116
- 期：32
- 页码：9611-9618
- 全文大小：457K
- 年卷期：v.116,no.32(August 16, 2012)
- ISSN：1520-5207
文摘
Small-angle X-ray scattering experiments of two monoclonal antibodies (mAbs) were performed as a function of Hofmeister salt type and concentration including 100 mM Na2SO4, 100鈥?00 mM of NaSCN, or 100鈥?00 mM arginine chloride at pH 6.0 to yield information on the effects of cosolutes on mAb solution conformation and flexibility. Minimal selected ensemble (MSE) procedures used to reconstruct the SAXS form factors revealed that both IgG1 mAbs exist in a conformational equilibrium with two subpopulations that vary in overall shape and size. The 鈥渃losed鈥?mAb conformation is characterized by a maximum dimension of 155 脜 and shorter distances between Fab鈥揊ab and Fab鈥揊C domains. The 鈥渙pen鈥?mAb conformation has a maximum dimension of 175 脜 and an increase in the interdomain distances with concomitant increases in overall mAb flexibility. Analysis of the distribution of shapes and sizes of mAb structures within the conformational equilibrium indicates that they remain essentially unchanged under conditions with a broad range of chaotropic and kosmotropic salts including 100鈥?00 mM NaSCN and 100 mM Na2SO4. Analysis of the conformations within each MSE population under various conditions reveals a striking similarity between many of the MSE structures, IgG crystal structures, and single-molecule imaging studies; MSE analysis of mAb form factors also identified an overall relaxation of the mAb structure unique to solution conditions containing arginine chloride, characterized by an increased maximum dimension and a shift toward the population of the 鈥渙pen鈥?mAb conformation. Our results provide the first comprehensive characterization of mAb conformational diversity in solution and are of direct relevance to understanding the effects of solution conditions on protein structural dynamics and stability.