Surface-induced assembly of apolipoprotein A-I: Implications for symmetry-driven non-cooperative clustering

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• 作者：Sidney Winford ; Moriah Tobin¹ ; Eitan Gross ; ^{exg004@uark.edu}
• 关键词：A1. Atomic force microscopy ; A1. Biomaterials ; A2. Growth from solutions ; B1. Biological macromolecules
• 刊名：Journal of Crystal Growth
• 出版年：2012
• 期刊代码：49_00220248
• 类别：ch
• 出版时间：15 March, 2012
• 卷：343
• 期：1
• 页码：38-44
• 文件大小：737 K

摘要

In condensed matter physics the geometry of a crystal is determined by the mechanism of condensation. In biology, the link between clustering mechanisms and the shape of a protein crystal is not well defined. To gain more insight into the problem, we studied clustering of apolipoprotein A-I (apo A-I) on a solid surface using AFM. The amyloidogenic protein apo A-I is the main protein component of high density lipoprotein and thus reduces the risk of atherosclerosis. We found that apo A-I clustered to form nano-scale, symmetrical clusters on mica. Statistical analysis of size distribution for several thousand clusters suggested that the clustering reaction followed a non-cooperative kinetic scheme characterized by a single equilibrium constant of 0.92路10⁶ M^鈭? and a change in free energy (螖G) of 鈭?.03 kJ mole^鈭?/residue. This is close to 螖G of鈭?.04 kJ mole^鈭?/residue for apo A-I binding to phospholipid membrane; and 30-fold smaller than 螖G for 尾-amyloid formation by apo A-I. The high symmetry of the clusters is consistent with an isotropic diffusion coefficient of protein monomers on the surface of the substrate. This previously unrecognized link between protein clustering mechanism and the symmetry of the growth pattern may have important implications in medicine, pharmaceutics and polymer science.