Fig. 3: Cryo-EM structures of BA.1 spike protein in complex with 1H1 RmAbs.

a, b the overall cryo-EM structures of the BA.1 spike-1H1 Fab complexes. a class I, 3.41 Å, revealing binding of 1H1 to RBDs in the “3 semi-up” state; b class II, 3.70 Å, revealing binding of 1H1 to RBDs in “1 semi-up/2 up” state. c, d the tilt angle of the semi-up (c) and up (d) BA.1 RBDs are defined by the angle between the long axis of RBD (red line) and its projection on the horizontal plane (black ellipse)³⁷. e a close-up view of a 3-fold symmetric conformation with three 1H1 Fabs bound to the “3 semi-up” RBDs in class I. f a close-up view of an asymmetric conformation with three Fabs bound to the “1 semi-up/2 up” RBD conformation in class II. g superposition of the BA.1 RBD-1H1 Fab model to a down RBD of the spike trimer demonstrates that 1H1 cannot bind to a down RBD because of steric clashes by N165 glycan on the adjacent NTD. h, superposition of the local-refined RBD-ACE2 model to that of BA.1 RBD-1H1 Fab model shows no steric hindrance between 1H1 Fab and ACE2. i superposition of the local-refined RBD-ACE2 model to that of BA.1 semi-up RBD in class I shows a steric hindrance between ACE2 and an adjacent semi-up RBD. j, k superposition of the local-refined RBD-ACE2 model to that of BA.1 semi-up RBD_A (j, left), up RBD_B (j, right) and up RBD_C (k) in class II shows steric hindrance between ACE2 and an adjacent RBD or a 1H1 Fab bound on the adjacent RBD.