Table 2. Measured binding kinetics data for wt and D374Y mutant PCSK9- LDL-R [12].

Fold differences between k_on and k_off for D374Y versus wt are shown in parenthesis, noting that the t_1/2 of the bound complex is similar to that of wt PCSK9, but considerably longer than that of the D374Y mutant (which is likely subject to k_off hijacking). The ratio of $k_{o{n}_{SS}}/k_{on}$ was calculated based on $k_{o{n}_{SS}}$ = 1x10⁸ M^-1 s^-1, corresponding to k_i = 1x10^-2 s^-1 (predicted from Eq 13 under the assumption that k_i = k_−i).

	wt		D374Y
	pH 7.4	pH5.3	pH 7.4	pH5.3
kon (M-1 s-1)	1.86x103	4.73x105	4.57x103 (+2.5-fold)	6.74x105 (+1.4-fold)
$k_{o{n}_{SS}}/k_{on}$	53,763	211	21,881	148
koff (s-1)	1.17x10-3	1.97x10-3	4.64x10-4 (-2.5-fold)	3.64x10-4 (-5.4-fold)
$k_{off}^{\prime }$ (s-1)	1.17x10-3	1.97x10-3	2.3x10-3§	2.3x10-3§
Kd (M)	628x10-9	4.19x10-9	101x10-9	0.54x10-9
Kd′ (M)	628x10-9	4.19x10-9	503x10-9	3.4x10-9

^§Similar clearance rates are assumed for both mutant and wt PCSK9.