Program in Structural Biology and Biophysics, Institute of Biotechnology, University of Helsinki, Viikinkaari 1, P.O. Box 65, FI-00014 Helsinki, Finland.
J Am Chem Soc. 2012 Apr 18;134(15):6660-72. doi: 10.1021/ja2114882. Epub 2012 Apr 10.
Filamins are actin-binding proteins that participate in a wide range of cell functions, including cell morphology, locomotion, membrane protein localization, and intracellular signaling. The three filamin isoforms found in humans, filamins A, B, and C, are highly homologous, and their roles are partly complementary. In addition to actin, filamins interact with dozens of other proteins that have roles as membrane receptors and channels, enzymes, signaling intermediates, and transcription factors. Filamins are composed of an N-terminal actin-binding domain and 24 filamin-type immunoglobulin-like domains (FLN) that form tail-to-tail dimers with their C-terminal FLN domain. Many of the filamin interactions including those for glycoprotein Ibα and integrins have been mapped to the region comprising FLN domains 16-21. Traditionally, FLN domains have been viewed as independent folding units, arranged in a linear chain joined with flexible linkers. Recent structural findings have shown that consecutive FLNs form more intricate superstructures. The crystal structure of filamin A domains 19-21 (FLNa19-21) revealed that domains 20 and 21 fold together and that the domain interaction can be autoregulatory. The solution structure of domains 18-19 showed a similar domain interaction, whereas domain pair 16-17 has a completely different domain packing mode. In this study, we characterize the domain organization of the FLNa domain sextet 16-21 using NMR spectroscopy. A structure model of this 60-kDa protein has been built using residual dipolar coupling restraints. RDCs and (15)N relaxation data have been used to characterize interdomain motions.
细丝蛋白是肌动蛋白结合蛋白，参与多种细胞功能，包括细胞形态、运动、膜蛋白定位和细胞内信号转导。人类中发现的三种细丝蛋白同工型，细丝蛋白 A、B 和 C，高度同源，它们的作用部分互补。除了肌动蛋白，细丝蛋白还与几十种其他蛋白质相互作用，这些蛋白质具有膜受体和通道、酶、信号中间物和转录因子的作用。细丝蛋白由一个 N 端肌动蛋白结合结构域和 24 个细丝蛋白型免疫球蛋白样结构域（FLN）组成，其 C 端 FLN 结构域与尾对尾二聚体形成。包括糖蛋白 Ibα和整合素在内的许多细丝蛋白相互作用已被映射到包含 FLN 结构域 16-21 的区域。传统上，FLN 结构域被视为独立的折叠单元，排列在由柔性接头连接的线性链中。最近的结构发现表明，连续的 FLN 形成更复杂的超结构。细丝蛋白 A 结构域 19-21（FLNa19-21）的晶体结构表明，结构域 20 和 21 折叠在一起，并且结构域相互作用可以是自调节的。结构域 18-19 的溶液结构显示出相似的结构域相互作用，而结构域对 16-17 具有完全不同的结构域包装模式。在这项研究中，我们使用 NMR 光谱学来表征 FLNa 结构域六联体 16-21 的结构域组织。使用残余偶极耦合约束构建了该 60 kDa 蛋白的结构模型。RDC 和（15）N 弛豫数据已用于表征结构域间运动。
