A proximal pair of positive charges provides the dominant ligand-binding contribution to complement-like domains from the LRP (low-density lipoprotein receptor-related protein)
A proximal pair of positive charges provides the dominant ligand-binding contribution to complement-like domains from the LRP (low-density lipoprotein receptor-related protein)
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DOI：
10.1042/bj20111867
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发表时间：
2012-04-01
影响因子：
4.1
通讯作者：
Dolmer, Klavs
中科院分区：
文献类型：
--
作者：
Gettins, Peter G. W.;Dolmer, Klavs
低密度脂蛋白受体相关蛋白LRP(Low-Density LipoProtein Receptor-Related Protein)可以结合多种结构不同的配体，由40个类似于钙离子依赖、富含二硫键的补体样重复序列(CRS)组成。虽然来自配体的赖氨酸残基与结合有关，但没有量化这种相互作用的能量贡献，因此它们在总体亲和力中的相对重要性，或精氨酸或组氨酸残基结合的能力。我们使用了LRP主要配体结合簇中四个具有代表性的CR结构域来确定与定义明确的小配体相互作用的能量学，这些小配体包括赖氨酸、精氨酸、组氨酸和天冬氨酸的甲酯，以及N端封闭的赖氨酸甲酯。我们发现，不仅赖氨酸结合良好，精氨酸和组氨酸也结合良好，当存在额外的近端正电荷时，约占蛋白配体(如PAI-1(纤溶酶原激活物抑制物-1))总结合能的一半。因此，两组这样的相互作用，两个CR结构域中的每一个都可以解释真实配体(如PAI-1)的几乎所有必要的结合能。对于CR结构域，序列DxDxD中的中心天冬氨酸残基使K-d收紧约20倍，而DxDDD并不更有效。总之，这些发现建立了确定蛋白质配体与LRP和其他LDLR(低密度脂蛋白受体)家族成员结合特异性的规则。
The LRP (low-density lipoprotein receptor-related protein) can bind a wide range of structurally diverse ligands to regions composed of clusters of similar to 40 residue Ca2+-dependent, disulfide-rich, CRs (complement-like repeats). Whereas lysine residues from the ligands have been implicated in binding, there has been no quantification of the energetic contributions of such interactions and hence of their relative importance in overall affinity, or of the ability of arginine or histidine residues to bind. We have used four representative CR domains from the principal ligand-binding cluster of LRP to determine the energetics of interaction with well-defined small ligands that include methyl esters of lysine, arginine, histidine and aspartate, as well as N-terminally blocked lysine methyl ester. We found that not only lysine but also arginine and histidine bound well, and when present with an additional proximal positive charge, accounted for about half of the total binding energy of a protein ligand such as PAI-1 (plasminogen activator inhibitor-1). Two such sets of interactions, one to each of two CR domains could thus account for almost all of the necessary binding energy of a real ligand such as PAI-1. For the CR domains, a central aspartate residue in the sequence DxDxD tightens the K-d by similar to 20-fold, whereas DxDDD is no more effective. Together these findings establish the rules for determining the binding specificity of protein ligands to LRP and to other LDLR (low-density lipoprotein receptor) family members.