Both calpain cleavage sites are located in predominantly unstructured regions.

<p>(A) The structures of the C-terminal ABS and the dimerisation domain of talin1 are incorporated into a model of the C-terminal region of the protein. The calpain2 cleavage site is indicated (blue line). (B–D) ¹H,¹⁵N HSQC spectra of the following talin1 polypeptides (150 µM); (B) Residues 2294–2541 spanning the C-terminal ABS and dimerisation domain (DD). The intense poorly dispersed peaks (red asterisks) relate to the 18 amino acid linker between the ABS and the DD (as deduced by comparison of the spectra of residues 2294–2491 and 2300–2482), and show that the linker is predominantly disordered. (C) Residues 400–480 - the linker between the talin1 head and rod that contains the calpain-cleavage site. The intense poorly dispersed signals in the centre of the spectrum indicate that the linker is predominantly unstructured. (D) Residues 309–655 containing the F3 FERM domain, the linker and the VBS1 rod domain. (E) A model of the linker region generated using MODELLER <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034461#pone.0034461-Eswar1" target="_blank">[50]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034461#pone.0034461-Sali1" target="_blank">[51]</a> showing that it can span ∼200 Å when fully extended. The calpain2 cleavage site (blue line) between Q433–Q434 is shown along with L432, which when mutated to a glycine, reduces calpain2 cleavage. The CDK5 phosphorylation site (S425) that regulates binding of Smurf1 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034461#pone.0034461-Huang1" target="_blank">[47]</a> is also shown.