What a Biochemistry Professor says

There are two talin genes in vertebrates, and both talin1 and talin2 (~270kDa; 2541 amino acids) are comprised of a globular N-terminal head (~50kDa) and a large flexible C-terminal rod (~220kDa). The talin head contains a FERM domain made up of F1, F2 and F3 domains, but is atypical in that F1 contains a large unstructured loop, and is preceded by an additional domain (F0) with homology to F1. As a result, the talin FERM domain adopts a more extended conformation than other FERM domains. The talin F3 FERM domain binds the cytoplasmic domains of β-integrin subunits and the hyaluronan receptor layilin, as well as the C-terminal region of PIPKIγ90, a splice variant of phosphatidylinositol(4) phosphate-5-kinase type Iγ which regulates the assembly of FAs. Genetic studies have recently identified the Drosophila protein Wech as an additional FERM domain binding partner, and since Wech also binds integrin-linked kinase (ILK), this may serve to cross-link integrin/talin to integrin/ILK complexes in FAs. The talin rod consists of ~62 helices that are organized into a series of amphipathic helical bundles, followed by a single C-terminal helix responsible for talin dimerisation. It contains an integrin-binding site, at least two actin-binding sites the best characterised of which is at the C-terminus, and multiple binding sites for vinculin, which itself has numerous binding partners including F-actin. The reader is referred to two recent reviews on talin from this laboratory.

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