The globular head domain of talin, a large multi-domain cytoplasmic protein, is required for inside-out activation of the integrins, a family of heterodimeric transmembrane cell adhesion molecules. Talin head contains a FERM domain that is composed of F1, F2, and F3 subdomains. A F0 subdomain is located N-terminus to F1. The F3 contains a canonical phosphotyrosine binding (PTB) fold that directly interacts with the membrane proximal NPxY/F motif in the integrin beta cytoplasmic tail. This interaction is stabilized by the F2 that interacts with the lipid head-groups of the plasma membrane. In comparison to F2 and F3, the properties of the F0F1 remains poorly characterized. Here, we showed that F0F1 is essential for talin-induced activation of integrin alphaLbeta2 (LFA-1). F0F1 has a high content of beta-sheet secondary structure, and it tends to homodimerize that may provide stability against proteolysis and chaotrope induced unfolding.
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