Table 1.

Binding Affinity between NPC2 and the NPC1 Variants Measured by ITC

NPC1 Variants	Kd (μM)	NPC1 Variants	Kd (μM)
FL (pH 7.5)	216.9 ± 35.3	ΔNTD	209.6 ± 19.9
FL (pH 6.0)	15.8 ± 1.2	L175A/L176A	162.9 ± 13.8
R518W	177.3 ± 15.0	Δlinker	266.0 ± 25.5
NTD	n/a	Q88A/Q92A/R96A	275.5 ± 14.3

Except for the first measurement, all the others were performed at pH 6.0. The indicated mutations were generated to full-length (FL) human NPC1. NTD: residues 1–252; ΔNTD: internal deletion of residues 25–257; ΔLinker: internal deletion of the Pro-rich segments ₂₄₉PKPQPPPPP₂₅₇.