Structure of dimeric fragments of the plakin domain

Resumen del póster presentado al XIVth Congress of the Spanish Biophysical Society, celebrado en Alcalá de Henares (Madrid-España) del 11 al 13 de junio de 2014.The plakin family consists of very large proteins involved in the interconnection of multiple systems of the cytoskeleton and their connection to adhesion complexes. In mammals the plakin family includes plectin, desmoplakin, the bullous pemphigoid antigen 1, the microtubule actin crosslinking factor 1, envoplakin, periplakin, and epiplakin. Plakins have a tripartite modular structure. The N-terminal region contains a conserved segment named the plakin domain (~1000 residues) that consists of up to nine spectrin repeats (SR1-SR9) and an SH3 domain; the plakin domains mediate the interaction with proteins in adhesion complexes. Downstream of the plakin domain extends a central rod domain (900 to 1300 residues) that mediates homo-dimerization via coiled-coil interactions. Finally, the C-terminal region contains binding sites for intermediate filaments. We have recently solved the crystal structure of a 39-residues fragment of the N-terminal region of the rod domain of plectin, which adopts a non-physiological antiparallel coiled-coil in the crystal, suggesting that the formation of parallel dimers requires larger segments of the rod domain. Here, we have created dimeric fragments of the plakin domain of plectin and desmoplakin by exchanging the large rod domain for the dimeric coiled-coil of GCN4. These fragments were analyzed by small angle x-ray scattering (SAXS) that confirmed the dimeric oligomerization state. Analysis of the SAXS data indicates that the inter-protomer contacts extend along the C-terminal segment of the plakin domain, but not in the N-terminal half of the plakin domain. These results have implications for the mechanical properties of plakins and their interaction with other proteins in adhesion complexes.Peer Reviewe