Figure 2.

T. brucei ABC proteins. ABC proteins share a nucleotide-binding domain (NBD), displaying conserved sequences among organisms. A typical full-size ABC transporter presents, in addition to the two NBDs, two transmembrane domains, which could be rearranged in direct (TMD–NBD) or reverse (NBD–TMD) order. Half-size transporter has only a TMD and an NBD, assuming that they form dimers or oligomers to transport substrates across membranes. The standardized names of ABC members in subfamilies according to the HUGO nomenclature are represented by forth letter, followed by number. For example, ABCB1 is subfamily B, member 1. RLI, L ribonuclease inhibitor domain. 4Fe-S, iron-sulfur cluster binding domain.