TABLE 2.

Kinetic and equilibrium constants for the binding of RAP D1D2 and mutants to LRP1

Kinetic constants were obtained by fitting the data to a model containing Scheme I and Scheme II (Fig. 2B). These experiments were performed in triplicate, and the values shown are the average ± S.E.

Protein	ka1	kd1	ka2	kd2	KD1a	KD2b	% Scheme Ic
	m−1 s−1	s−1	m−1 s−1	s−1	m	m
WT	1.1 ± 0.1 × 106	0.028 ± 0.002	3.2 ± 1.1 × 105	0.0017 ± 0.0001	1.1 ± 0.1 × 10−16	2.6 ± 0.1 × 10−8	52–92d
K60A	2.6 ± 0.4 × 106	0.074 ± 0.013	6.7 ± 3.3 × 105	0.0041 ± 0.0003	4.0 ± 1.5 × 10−16	2.6 ± 0.4 × 10−8	10–20
K191A	4.1 ± 0.9 × 106	0.029 ± 0.005	4.4 ± 2.8 × 105	0.0033 ± 0.0003	2.6 ± 1.6 × 10−16	7.3 ± 0.3 × 10−9	38

^a The equilibrium binding constant K_A1 was calculated using the following equation: K_A1 = (k_a1/k_d1)·(1 + (k_a2/ k_d2) and K_D1 was calculated as K_D1 = 1/K_A1.

^b The equilibrium binding constant K_A2 was calculated using the following equation: K_A2 = k_a1/k_d1 and K_D2 was calculated as K_D2 = 1/K_A2.

^c Percent of complex II that forms (bivalent binding, Fig. 2B, Scheme I) is shown.

^d For WT D1D2, the amount of complex II that forms is dependent upon D1D2 concentration (see Fig. 3).