Extended Data Table 2.

R.m.s.d. values of all atoms among apo and ligand-bound conformers

Structures aligned with the kissing loops
	3-way jct.	P1*	U48	U51	U74	Hinge	Latch	Kissing loops
apo2 vs. 4TZX	6.4	6.5	13.3	10.1	2.8	5.9	7.5	0.8
apo1 vs. 4TZX	6.2	10.3	11.5	10.0	2.8	7.8	6.8	0.8
apo1 vs. apo2	3.4	6.4	2.8	4.7	1.7	7.2	2.0	0.5
apo1 vs. IB	3.5	5.0	2.3	4.8	1.6	6.4	2.0	0.8
apo2 vs. IB	1.3	1.4	2.4	0.4	0.6	2.5	0.8	0.3
IB vs. 4TZX	5.6	6.6	12.2	9.9	3.2	5.4	6.5	0.89
Whole structure alignments
	3-way jct.	P1*	U48	U51	U74	Hinge	Latch	Kissing loops
apo2 vs. 4TZX	5.6	2.5	10.6	10.0	2.3	1.6	4.9	0.9
apo1 vs. 4TZX	5.6	3.4	7.9	10.6	2.3	1.7	4.8	0.8
apo1 vs. apo2	3.6	1.5	2.6	2.0	1.6	2.4	1.4	0.3
apo1 vs. IB	3.3	3.8	2.3	3.9	1.8	6.2	1.8	1.1
apo2 vs. IB	1.3	1.3	2.4	0.3	0.4	0.3	0.8	0.3
IB vs. 4TZX	5.5	4.1	10.7	10.9	2.4	5.1	6.4	1.4

^*The r.m.s.d. values (Å) of P1 when compared alone are among the three structures:

1.3 Å (apo2 versus bound); 0.9 Å (apo1 versus bound); 1.0 Å (apo2 versus apo1); 1.4 Å (IB versus bound); 1.3 Å (IB versus apo1); 1.3 Å (IB versus apo2).