Like in typical MRPs, there were several conserved motifs in the NBD1 of CsMRP4, such as an ATP-binding site (441GCxKSSx26Qx78DDx31N585), ABC transporter signature motif (528LSGGQKARIG537), Walker A/P-loop (438GPVGCGKS445), Walker B (548FLLLDD553), D-loop (556AAVD559), Q-loop/lid (470YMPQ473), and H-loop/switch region (581LLVTNQL587). These motifs play pivotal roles in transporting substrates via conformational changes between outward-facing and inward-facing forms. Dimerization of two NBDs forms the nucleotide-binding site between the Walker A/P-loop, Walker B, and ABC signature motif. The bound ATP is hydrolyzed to provide energy in order to efflux endogenous and xenobiotic substrates from cells to the extracellular milieu .