NMR assignment of the C-terminal actin-binding domain of talin

摘要

Talin is a large dimeric 270 kDa adapter protein which binds the cytoplasmic face of a subset of integrin beta-subunits and couples them to the actin cytoskeleton. Here we report the near complete ~(15)N, ~(13)C and ~1H chemical shift assignments forthe C-terminal actin-binding domain. Cellular interactions with the extracellular matrix are modulated via dynamic protein complexes associated with the cytoplasmic face of the integrin family of cell adhesion molecules. Talin is one of a number of cytoskeletal proteins including a-actinin, filamin, tensin and ILK implicated in linking members of the integrin family of ajS-heterodimeric cell adhesion molecules to F-actin (see Critchley 2000 for review). It is large (2541 amino acids) elongated (50-60 nm) protein composed of a globular head (residues 1-400) containing a PERM domain linked to a flexible rod (residues 482-2541) by a short linker sequence. The PERM F3 sub-domain contains a binding site for the beta-integrin cytoplasmic domain, and recent structural studies have provided a detailed understanding of how F3 recognises both the NP x Y motif and membrane proximal sequences within the beta-integrin cytodomain (Wegener et al. 2007). The talin rod is made up of a series of amphipathic helical bundles, a number of which contain binding sites for the cytoskeletal protein vinculin which is thought to stabilise focal adhesions, possibly by cross-Unking talin to F-actin. The C-terminal region of talin (residues 2300-2541) contains the major binding site for F-actin (Hemmings et al. 1996) that is homologous to that in the yeast protein Slap2 and the Hun-tingtin interacting protein HIP1, and the related protein Hip 1R. This highly conserved domain has been referred to as an I/LWEQ motif (McCann and Craig 1997) or more recently the THATCH (talin-Hipl/R/Sla2p actin tethering C-terminal homology) core domain (Brett et al. 2006).