Identification by integrated computer modeling and light scattering studies of an electrostatic serum albumin-hyaluronic acid binding site
Identification by integrated computer modeling and light scattering studies of an electrostatic serum albumin-hyaluronic acid binding site
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DOI：
10.1021/bm005656z
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发表时间：
2001-06-01
影响因子：
6.2
通讯作者：
Mattison, KW
中科院分区：
文献类型：
--
作者：
Grymonpré, KR;Staggemeier, BA;Mattison, KW
动态光散射和比浊法，进行透明质酸（HA）和牛或人血清白蛋白（SA）在固定的离子强度（I）的解决方案，揭示了一个临界pH值对应的发病HA-SA可溶性复合物的形成。随后pH降低至pH（c）以下，对应于蛋白质净正电荷的增加，导致复合物的相分离。pH（c）对I的敏感性表明在此过程中静电相互作用占首要地位。由于pH（c）总是高于HA的pK（a），因此这些效应可以归因于蛋白质电荷的影响。在对应于初始结合、相分离和非相互作用的pH，I条件下，使用德尔菲（MSI）模拟HSA周围的静电势。在所有初始结合条件下（即，pH（c），在不同的I）下，出现了距蛋白质货车德瓦耳斯表面5埃的正电位的相同区域。这种独特的结构域随着pH或I的降低而增强（对应于更强的结合），并且随着pH或I的增加而减弱（即，在非相互作用条件下）。该结构域的大小和低曲率可以容易地容纳HA的12 nm（十聚体）序列。简单的静电考虑表明，这种复合物的形成的静电结合能的ca。1 kT，与初始复合物形成的条件一致。我们认为，这种弱的静电结合可能表征其他蛋白质-糖胺聚糖对的非特异性相互作用。
Dynamic light scattering and turbidimetry, carried out on solutions of hyaluronic acid (HA) and bovine or human serum albumin (SA) at fixed ionic strength (I), revealed a critical pH corresponding to the onset of HA-SA soluble complex formation. Subsequent reduction of pH below pH(c), corresponding to an increase in protein net positive charge, results in phase separation of the complex. The sensitivity of pH(c) to I indicated the primacy of electrostatic interactions in this process. Since pH(c) was always above the pK(a) of HA, these effects could be attributed to the influence of protein charge, The electrostatic potential around HSA was modeled using DelPhi (MSI) under pH, I conditions corresponding to incipient binding, phase separation, and noninteraction. At all incipient binding conditions (i.e., pH(c), at varying I), an identical region of positive potential 5 Angstrom from the protein van der Waals surface appeared. This unique domain intensified with a decrease in pH or I (corresponding to stronger binding), and diminished with an increase in pH or I (i.e., at noninteracting conditions). The size and low curvature of this domain could readily accommodate a 12 nm (decamer) sequence of HA. Simple electrostatic considerations indicate an electrostatic binding energy for the formation of this complex of ca. 1 kT, consistent with the condition of incipient complex formation. We suggest that such weak electrostatic binding may characterize nonspecific interactions for other protein-gylcosaminoglycan pairs.