Coronavirus spike structures display a range of conformations, with much of the variability due to hinge-like motions of the receptor binding domain (RBD), which is key to receptor binding and antibody recognition. Automatic clustering of spike structural similarities was used to annotate the RBD-open (or up) and RBD-closed (or down) states for all spike structures. These are updated periodically, as more spike structures are released.
	O: Open conformation
	C: Closed conformation
	-: RBD not present