Structural Determinants of Integrin Recognition by Talin Begoña Garcı́a-Alvarez, José M de Pereda, David A Calderwood, Tobias S Ulmer, David Critchley, Iain D Campbell, Mark H Ginsberg, Robert C Liddington  Molecular Cell  Volume 11, Issue 1, Pages 49-58 (January 2003) DOI: 10.1016/S1097-2765(02)00823-7

Figure 1 Structure of the F2+F3 Domain of Talin (A) Domain organization and functional sites of full-length talin. A calpain II cleavage site separates the head and tail domains. The three subdomains of the classical FERM domain are represented by white, blue, and red boxes. Functional assignments are indicated by horizontal bars. (B) Stereo ribbon representation of the F2+F3 structure, with secondary structure indicated. Figures were generated using the programs MOLSCRIPT (Kraulis, 1991), RASTER3D (Merritt and Murphy, 1994), SPOCK (Christopher, 1998), or BOBSCRIPT (Esnouf, 1997). (C) Structure-based sequence alignment of the F2+F3 region of talin with the human FERM proteins moesin (SwissProt accession number P26038), radixin (P35241), merlin (P35240), band 4.1 (P11171), and Focal Adhesion Kinase; and the PTB domains of X11 (Q02410) and IRS-1 (P35568). The large insertions in the β1-β2 and β6-β7 loops of X11 are not shown, and are represented by dots. The secondary structure elements of talin are indicated: α helices and 310 helices as rectangles, and β strands as arrows. Residues directly participating in β3 integrin binding to talin are indicated by boxes, and mutations that are critical for integrin binding are marked in red. (D) Stereo representation of the F3 domain (Cα), showing the invading N-terminal arm (all atom) from a neighboring molecule in the crystal lattice. Molecular Cell 2003 11, 49-58DOI: (10.1016/S1097-2765(02)00823-7)

Figure 2 Structural Studies of Talin-Integrin Binding (A) Ratio of 2D NMR 1H-15N signal intensities of the full-length β3 tail, fused to a coiled-coil construct, in the absence, I0, and presence, I, of F2+F3. Pronounced reductions in peak intensity in the presence of F2+F3, i.e., low I/I0 ratios were observed for some residues, indicating a perturbation of the associated amino acid residue by the interaction with F2+F3. The absence of reductions of peak intensity within the coiled-coil region (residues 3–39) confirms the specificity of the interactions. The most strongly affected regions in the vicinity of the NPxY motif are boxed, and the inset shows aligned sequences of β integrins and layilin (Lay1 and Lay2). The residue in position −8 of integrins (−6 in layilin) is in a blue box, while the NPXY motif is in a yellow box. The observed effects are strongly dependent on the integrity of the NPxY motif, as demonstrated by the abolition of these effects by the Y747A substitution. The significance of the spectral changes observed in the membrane proximal region is unclear. (B) Surface representation of the F3 subdomain of talin, colored by electrostatic potential (blue for positive charge and red for negative). The β3 integrin ligand, residues 738–747, is shown as sticks. Integrin residues are labeled in green, while residues of talin are labeled on the surface. (C) Stereo close-up of the integrin-talin interaction as observed in the β3(739-749)-talin chimera; the talin backbone is in gray, integrin in yellow. Residue numbers are those for authentic talin (gray) and integrin (green) sequences. For the latter, numbers in parenthesis refer to the position with respect to the NPLY tyrosine. There are no significant differences with β3(739-749)-talin. The main chain of one residue derived from the construct upstream of W739 is also shown, as it has good electron density in all of the chimeras. A partially buried water molecule is indicated with (ω) and key H bonds with dotted lines. Molecular Cell 2003 11, 49-58DOI: (10.1016/S1097-2765(02)00823-7)

Figure 3 Comparison of FERM F3 and PTB Domain Interactions Stereo Cα plot comparing the F3 subdomain of talin and the integrin sequence (red), the F3 subdomain of moesin and the β strand of the C-terminal tail (green), and the PTB domain of X11 with the β-APP bound (blue). The structures were superposed by aligning the Cα atoms of 39 residues in the β sandwich. The ligands are shown as thick lines. The tyrosine sidechains of the NPxY motifs of integrin and β-APP are also shown. For clarity, insertions in the X11 structure absent in FERM domains are not shown. Residue numbering is for talin. Molecular Cell 2003 11, 49-58DOI: (10.1016/S1097-2765(02)00823-7)

Figure 4 Structure-Based Mutagenesis of the Talin At left, binding of talin mutants to full-length β3 tail. Recombinant F2+F3 containing the indicated mutation was incubated with the integrin β3 cytoplasmic domain model protein; following washing, the bound protein was detected by SDS-PAGE. Note the absence of binding to β3(Y747A) and αIIb cytoplasmic domain model proteins and the equal loading (rightmost column) of each mutant. The bottom row depicts the equal loading of each model tail protein as judged by SDS-PAGE. At right, residues mutated in this study are mapped onto the surface of the talin F3 domain, with hydrophobic residues colored yellow. The K357A mutation (green) does not affect binding, while alanine substitution of R358, W359, and I396 (red) reduce binding. Molecular Cell 2003 11, 49-58DOI: (10.1016/S1097-2765(02)00823-7)