From the Department of Biological and Environmental Science and Nanoscience Center, University of Jyväskylä, P. O. Box 35, Survontie 9, 40014 Jyväskylä.
J Biol Chem. 2014 Mar 21;289(12):8588-98. doi: 10.1074/jbc.M113.537456. Epub 2014 Jan 27.
Immunoglobulin-like (Ig) domains are a widely expanded superfamily that act as interaction motifs or as structural spacers in multidomain proteins. Vertebrate filamins (FLNs), which are multifunctional actin-binding proteins, consist of 24 Ig domains. We have recently discovered that in the C-terminal rod 2 region of FLN, Ig domains interact with each other forming functional domain pairs, where the interaction with signaling and transmembrane proteins is mechanically regulated by weak actomyosin contraction forces. Here, we investigated if there are similar inter-domain interactions around domain 4 in the N-terminal rod 1 region of FLN. Protein crystal structures revealed a new type of domain organization between domains 3, 4, and 5. In this module, domains 4 and 5 interact rather tightly, whereas domain 3 has a partially flexible interface with domain 4. NMR peptide titration experiments showed that within the three-domain module, domain 4 is capable for interaction with a peptide derived from platelet glycoprotein Ib. Crystal structures of FLN domains 4 and 5 in complex with the peptide revealed a typical β sheet augmentation interaction observed for many FLN ligands. Domain 5 was found to stabilize domain 4, and this could provide a mechanism for the regulation of domain 4 interactions.
免疫球蛋白样 (Ig) 结构域是一个广泛扩展的超家族，在多功能蛋白中充当相互作用基序或结构间隔物。脊椎动物细丝蛋白 (FLN) 是一种多功能肌动蛋白结合蛋白，由 24 个 Ig 结构域组成。我们最近发现，FLN 中 C 端杆 2 区的 Ig 结构域相互作用形成功能结构域对，其中与信号和跨膜蛋白的相互作用受弱肌球蛋白收缩力的机械调节。在这里，我们研究了 FLN N 端杆 1 区第 4 结构域周围是否存在类似的结构域间相互作用。蛋白质晶体结构揭示了 3、4 和 5 结构域之间的新型结构域组织。在这个模块中，结构域 4 和 5 相互作用相当紧密，而结构域 3 与结构域 4 具有部分柔性界面。NMR 肽滴定实验表明，在三结构域模块内，结构域 4 能够与来自血小板糖蛋白 Ib 的肽相互作用。FLN 结构域 4 和 5 与肽复合物的晶体结构揭示了许多 FLN 配体中观察到的典型 β 片层增强相互作用。结构域 5 被发现稳定了结构域 4，这可能为结构域 4 相互作用的调节提供了一种机制。
