Figure 4.

Allostery in theb I domain and comparison with α I domain. a, Overview of motions in the β₃ I and hybrid domains. Non-moving parts of the backbone are shown as a grey worm. Moving segments shown as Cα-traces are from unliganded-closed α_Vβ₃ (gold), liganded-closed α_Vβ₃ (magenta) and liganded-open α_IIbβ3 (cyan). The direction of movement is shown with arrows. b, Comparison witha I domains. The moving segments of unliganded-closed (gold) and pseudoliganded-open (cyan) α_M I domains^25,26 and their MIDAS metal ions are shown as in a and in the same orientation. c, Hydrophobic ratchet pockets underlying the β6–α 7 loop anda 1-helix. The unliganded-closed (orange) and liganded open (cyan) β 1–α 1 loop, α 1-helix, α 1–b 2 loop and β 6–α 7 loop anda 7-helix are shown as worm traces with key side chains, the Met 335 carbonyl and metal ions in the same colour. The rest of the domain is shown as a grey surface, except for hydrophobic pocket residues Tyr 116, Val 247, Thr 249, Ile 307, Ala 309 and Thr 311, which are shown as a black surface. d,β₃ I domain metal coordination sites in liganded-open α_IIbβ3 (cyan) and unliganded-closed α_Vβ₃ (yellow). LIMBS, MIDAS and ADMIDAS positions are shown left to right in similar orientation as in a. The LIMBS and MIDAS were not occupied in the unliganded-closed structure⁷; for reference, metal ions at these sites are shown from the liganded-closed structure⁸. In a–d, metal ions are shown as spheres in the same or a similar (d) colour as their associated backbone. e, Distances between Ca atoms in the three superimposed β I domains, smoothed by averaging at each residue over a 3-residue window.