Substrate binding reorganizes the energetic landscape of Plasmodium falciparum hexose transporter PfHT1

Abstract

Malaria parasites depend on the Plasmodium falciparum hexose transporter PfHT1 for sugar uptake, yet how substrate binding reshapes transporter energetics and kinetics of sugar transport remains poorly understood. Here, we investigate how glucose reorganizes the conformational landscape, transition pathways, and residue interaction network underlying membrane transport. Using over 800 s of adaptive molecular dynamics simulations combined with Markov state models, transition-path theory, residue-contact analysis, and graph attention learning, we reconstruct the apo and glucose-bound conformational cycles. We show that glucose selectively stabilizes productive outward-facing, occluded, and inward-facing conformations, reshapes transition kinetics, and channels reactive flux through the occluded state. We identify TM7b helix cracking as a local structural transition coupled to extracellular-gate closure and substrate progression, providing a flexible connection between the binding pocket and global alternating access. Experimental testing of mechanistically critical residues validated their functional importance in PfHT1-dependent sugar utilization. Together, these results show how substrate binding reorganizes the energetic, kinetic, and interaction landscape of membrane transport and establish a transferable framework for studying transporter mechanisms.