Activation of a vinculin-binding site in the talin rod involves rearrangement of a five-helix bundle

Abstract

The interaction between the cytoskeletal proteins talin and vinculin plays a key role in integrin-mediated cell adhesion and migration. We have determined the crystal structures of two domains from the talin rod spanning residues 482-789. Talin 482-655, which contains a vinculin-binding site (VBS), folds into a five-helix bundle whereas talin 656-789 is a four-helix bundle. We show that the VBS is composed of a hydrophobic surface spanning five turns of helix 4. All the key side chains from the VBS are buried and contribute to the hydrophobic core of the talin 482-655 fold. We demonstrate that the talin 482-655 five-helix bundle represents an inactive conformation, and mutations that disrupt the hydrophobic core or deletion of helix 5 are required to induce an active conformation in which the VBS is exposed. We also report the crystal structure of the N-terminal vinculin head domain in complex with an activated form of talin. Activation of the VBS in talin and the recruitment of vinculin may support the maturation of small integrin/talin complexes into more stable adhesions.

Subcellular Localization of Talin Is Regulated by Inter-domain Interactions

“…5C, 40 Ϯ 11 and 57 Ϯ 14%, respectively). These data indicate that the loss of the Tln1(466 -787) fragment, a region of the talin rod containing two helical bundles (VBS1 and VBS2a) that comprise vinculin-binding sites (44), leads to plasma membrane localization. FL ⌬E).…”

“…NMR analysis revealed a second inter-domain interaction between THD and a pair of vinculin-binding ␣-helical bundles in the talin rod termed VBS1/2a (Tln1(482-787)); mutations that disrupt the VBS1/2a-F2F3 interaction led to plasma membrane localization of talin. Furthermore, expression of the vinculin head domain (VinHD; vinculin(2-258)) that binds to VBS1/2a (41)(42)(43)(44) results in talin recruitment to the plasma membrane, accounting for the capacity of VinHD to induce talin-dependent integrin activation (43,45). Thus, specific contacts between THD and helical bundles in the talin rod control the subcellular localization of talin.…”

The Serine-rich Domain from Crk-associated Substrate (p130 ) Is a Four-helix Bundle

“…Whereas FAK contains a single fourhelix bundle, namely the FAT domain (32,33), vinculin and ␣-catenin are composed of multiple bundles (30,31,35,57). Most recently, talin was also shown to employ ␣-helical bundles in its architecture (36). Despite limited sequence homology, SRR-B is structurally similar to some of these helix bundles, as shown in Fig.…”

The tale of two talins – two isoforms to fine‐tune integrin signalling

“…The vinculin‐binding determinants lay on one side of each vinculin‐binding helix 89. However, the VBS are buried within the rod domains and are only exposed by mechanical force (Fig.…”