Fig. 4: Structural changes upon ligand binding.

a Comparison of α6β1 headpiece conformations before and after ligand binding. The crystal structure of unliganded α6β1 headpiece (gray) was superposed at the βI domain onto the cryo-EM structure of the LM511 complex (color-coded as in Fig. 3b). An expanded view near the βI MIDAS (boxed) is shown in the right. The global conformational rearrangement (i.e., a swing-out of the β1 hybrid domain) and the local conformational rearrangement (i.e., shifts in α1 and α7 helices) are denoted by red and orange arrows, respectively. The N-acetylglucosamine (NAG) residue attached to N343 is shown in stick model. b. HUTS-4 cannot bind to the tucked hybrid domain in the closed headpiece conformation. The hybrid domain and HUTS-4 in the cryo-EM structure (color-coded as in Fig. 3b) was superposed at the hybrid domain onto the crystal structure of closed α6β1 headpiece (gray). c LM511 does not undergo conformational change. The crystal structure of tLM511 (PDB ID: 5xau, gray) was superposed onto the cryo-EM structure (color-coded as in Fig. 3b) at the LG1-3 domains.