Substrate binding and lipid-mediated allostery in the human organic anion transporter 1 at the atomic-scale

The Organic Anion Transporter 1 is a membrane transporter known for its central role in drug elimination by the kidney. h OAT1 is an antiporter translocating substrate in exchange for α -ketoglutarate. The understanding of h OAT1 structure and function remains limited due to the absence of resolved structure of h OAT1. Benefiting from conserved structural and functional patterns shared with other Major Facilitator Superfamily transporters, the present study intended to investigate fragments of h OAT1 transport function and modulation of its activity in order to make a step forward the understanding of its transport cycle. μs -long molecular dynamics simulation of h OAT1 were carried out suggesting two plausible binding sites for a typical substrate, adefovir, in line with experimental observations. The well-known B-like motif binding site was observed in line with previous studies. However, we here propose a new inner binding cavity which is expected to be involved in substrate translocation event. Binding modes of h OAT1 co-substrate α -ketoglutarate were also investigated suggesting that it may binds to highly conserved intracellular motifs. We here hypothesize that α -ketoglutarate may disrupt the pseudo-symmetrical intracellular charge-relay system which in turn may participate to the destabilisation of OF conformation. Investigations regarding allosteric communications along h OAT1 also suggest that substrate binding event might modulate the dynamics of intracellular charge relay system, assisted by surrounding lipids as active partners. We here proposed a structural rationalisation of transport impairments observed for two single nucleotide polymorphisms, p.Arg50His and p.Arg454Gln suggesting that the present model may be used to transport dysfunctions arising from h OAT1 mutations. Highlights Adefovir has at least two binding pockets on h OAT1 in the outward-facing conformation. The highly conserved B-motif within MFS is strongly involved in substrate binding. α -Ketoglutarate binds to the intracellular domain of h OAT1 and destabilizes its OF conformation. The lipid membrane bilayer plays an active role in the allosteric communication between intracellular and extracellular domains of h OAT1. Graphical Abstract The present work (from left): ( i ) reveals binding modes of adefovir (top) and α -ketoglutarate (bottom) to h OAT1; ( ii ) maps Single Nucleotide Polymorphisms on outward-facing (top) and inward-facing (bottom) conformation of h OAT1; ( iii ) asses the allosteric effect of lipidic environment and presence of substrates.