Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208, USA.
Blood. 2010 May 20;115(20):4093-101. doi: 10.1182/blood-2009-11-255604. Epub 2010 Jan 25.
Maintenance of membrane integrity and organization in the metazoan cell is accomplished through intracellular tethering of membrane proteins to an extensive, flexible protein network. Spectrin, the principal component of this network, is anchored to membrane proteins through the adaptor protein ankyrin. To elucidate the atomic basis for this interaction, we determined a crystal structure of human betaI-spectrin repeats 13 to 15 in complex with the ZU5-ANK domain of human ankyrin R. The structure reveals the role of repeats 14 to 15 in binding, the electrostatic and hydrophobic contributions along the interface, and the necessity for a particular orientation of the spectrin repeats. Using structural and biochemical data as a guide, we characterized the individual proteins and their interactions by binding and thermal stability analyses. In addition to validating the structural model, these data provide insight into the nature of some mutations associated with cell morphology defects, including those found in human diseases such as hereditary spherocytosis and elliptocytosis. Finally, analysis of the ZU5 domain suggests it is a versatile protein-protein interaction module with distinct interaction surfaces. The structure represents not only the first of a spectrin fragment in complex with its binding partner, but also that of an intermolecular complex involving a ZU5 domain.
真核细胞通过将膜蛋白锚定到一个广泛而灵活的蛋白质网络上来维持膜的完整性和组织。 spectrin 是该网络的主要成分，通过衔接蛋白锚蛋白锚定到膜蛋白上。为了阐明这种相互作用的原子基础，我们确定了人βI- spectrin 重复序列 13 到 15 与人类锚蛋白 R 的 ZU5-ANK 结构域复合物的晶体结构。该结构揭示了重复序列 14 到 15 在结合中的作用，以及沿界面的静电和疏水贡献，以及 spectrin 重复序列的特定取向的必要性。我们使用结构和生化数据作为指导，通过结合和热稳定性分析来表征单个蛋白质及其相互作用。除了验证结构模型外，这些数据还深入了解了与细胞形态缺陷相关的一些突变的性质，包括那些在遗传性球形红细胞增多症和椭圆形红细胞增多症等人类疾病中发现的突变。最后，对 ZU5 结构域的分析表明，它是一种具有独特相互作用表面的多功能蛋白-蛋白相互作用模块。该结构不仅代表了与配体结合的 spectrin 片段的第一个结构，而且还代表了涉及 ZU5 结构域的分子间复合物的结构。
