Table 2.

Summary of measured binding of 7SK with HEXIM at different peptide concentrations measured as percentage of complex formation (28), and of the observed behaviour from simulations for wild type and mutants

Molecule	Binding at 0.3 μM	Binding at 0.8 μM	Observed behaviour in simulations
WT	80%	90%	Mainly M2, U63 outward
A39G–U68C	80%	90%	Mainly M2, flexible U63.
A39U–U68A	60%	95%	Mainly M2, flexible U63.
delU63	65%	80%	M2 and extended, some U40–U68
U41C	50%	80%	Few M2, some structures with U63 outward
A39G	40%	80%	Mainly M2, U63 inward
doubleCG	30%	70%	Mainly extended, U40–U68 pair, few M2
doubleUA	30%	70%	Mainly extended, U40–U68 pair, few M2
A39U	30%	60%	Mainly extended, some U40–U68, U63 inward
U40C	20%	65%	Few M2, U63 across the groove
U40C-U41C	15%	45%	Few M2, C40 and C41 unavailable

Quantitative details of the simulations for mutants can be found in Supplementary Table S1.