Interaction of two β-subunits when one of them is fixed and the other is steered.

<p>(a) (top left) Two β-subunits are placed 5 nm apart from one another (helix backbone: yellow; hydrophobic residues: orange; acidic residues: red; basic residues: blue) and equilibrated in a plasma membrane patch (point representation). Membrane-proximal, cytoplasmic residue W739 on the steered monomer and residues F727 and F730 on the constrained monomer interact with the plasma membrane strongly enough to introduce a kink between the cytoplasmic and transmembrane domains of each monomer. (top right) Steered residue W739, and constrained residues F727 and F730 form hydrophobic bonds, shaping a stable conformation. (inset) The NPLY sequences, where talin-integrin interaction occurs, are highlighted. (b) Distance between the centers of mass of the monomers diminishes linearly until the two monomers interact at distance 3.6 nm. (c) The SMD force increases as the steered monomer comes closer, and the interaction eventually occurs at 1500 pN. The legend illustrates the steered β-monomer (blue), being pulled toward the constrained monomer while they are embedded in a lipid bilayer.