Six-transmembrane helical domain 2 (TMD2) of the yeast Vmr1p, Ybt1p and Nft1; ABCC subfamily
This group includes the six-transmembrane domain 2 (TMD2) of the yeast Vmr1p, Ybt1p and Nft1, all of which are ABC transporters of the MRP (multidrug resistance-associated protein) subfamily (ABCC). Yeast ABCC (also termed MRP/CFTR) subfamily includes six members (Ycf1p, Bpt1p, Ybt1p/Bat1p, Nft1p, Vmr1p, and Yor1p), of which three members (Ycf1p, Bpt1P and Yor1p) are not included here. While Yor1p, an oligomycin resistance ABC transporter, has been shown to localize to the plasma membrane, the other 4 members (Ycf1p, Bpt1p, Ybt1p/Bat1p, Nft1p and Vmr1p) have been shown to localize to the vacuolar membrane. Ybt1p is originally identified as a bile acid transporter and regulates membrane fusion through Ca2+ transport modulation. Ybt1p also plays a part in ade2 pigment transport. Moreover, Ybt1p has been recently shown to translocate phosphatidylcholine from the outer leaflet of the vacuole to the inner leaflet for degradation and choline recycling. Vmr1p, a vacuolar membrane protein, participates in the export of numerous growth inhibitors from the cell, such as cycloheximide, 2,4-dinitrophenole, cadmium and other toxic metals. Nft1p is not well-characterized, but it is proposed to be regulate Ycf1p, which is involved in heavy metal detoxification.
Comment:All members of this ABC transporter family contain 6 alpha-helices in each transmembrane domain (TMD) for a total of 12 TM segments in the complete transporter.
Jiyao W et al.(2023). "The conserved domain database in 2023.",