Crespi, V. | bioRxiv Science

bioRxiv2022

Computational and structural insights into the pre- and post-hydrolysis states of multidrug resistance associated protein 1 in lipid bilayer membranes

ATP-binding cassette C-family drug membrane transporters play an important role in local pharmacokinetics, i.e., drug concentration in cellular compartments. From the structural point of view, only the bovine ortholog of the multidrug-resistance associated protein 1 (bMRP1) has been resolved. We here used s-scaled molecular dynamics simulations to investigate the structure and dynamics of bMRP1 in pre- and post-hydrolysis functional states. The present work aims to examine the slight but likely relevant structural differences between pre- and post-hydrolysis states of outward-facing conformations as well as the interactions between MRP1 and the surrounding lipid bilayer. Global conformational dynamics show unfavourable extracellular opening associated with nucleotide binding domain dimerization indicating that the post-hydrolysis state adopts a close-cleft conformation rather than an outward-open conformation. Our present simulations also highlight persistent interactions with annular cholesterol molecules and the expected active role of lipid bilayer in the allosteric communication between distant domains of MRP1 transporter.

pharmacology and toxicology↗

bioRxiv2022

On the interplay between lipids and asymmetric dynamics of an NBS degenerate ABC transporter

Multidrug resistance-associated proteins are ABC C-family exporters. They are crucial in pharmacology as they transport various substrates across membranes. However, the role of the degenerate nucleotide-binding site (NBS) remains unclear likewise the interplay with the surrounding lipid environment. Here, we propose a dynamic and structural overview of MRP1 from ca. 110 {micro}s molecular dynamics simulations. ATP binding to NBS1 is likely maintained along several transport cycles. Asymmetric NBD behaviour is ensured by lower signal transduction from NBD1 to the rest of the protein owing to the absence of ball-and-socket conformation between NBD1 and coupling helices. Even though surrounding lipids play an active role in the allosteric communication between the substrate-binding pocket and NBDs, our results suggest that lipid composition has a limited impact, mostly by affecting transport kinetics. We believe that our work can be extended to other degenerate NBS ABC proteins and provide hints for deciphering mechanistic differences among ABC transporters.

biophysics↗