Figure 1. Location of the nine native Cys residues in Pgp.

Cys residues (red) are shown in two views of the Pgp crystal structure (3G61). Cys⁴²⁷ is located in the N-terminal NBD (NBD1, blue), while Cys¹⁰⁷⁰, Cys¹¹²¹ and Cys¹²²³ are in the C-terminal NBD (NBD2, green). Cys¹³³, Cys⁷¹³ and Cys⁹⁵² are located in the membrane bound portion of the TMDS. Cys⁶³⁸ and Cys⁶⁶⁹ are in the flexible linker between NBD1 and TMD2 that was not resolved in the Pgp crystal structure. Dotted lines delineate the approximate location of the membrane bilayer. ICL, intracellular loop.