On the mechanism of K+ transport through the inter-subunit tunnel of KdpFABC.

ABSTRACT: KdpFABC is an ATP-dependent membrane complex that enables prokaryotes to maintain potassium homeostasis under potassium-limited conditions. It features a unique hybrid mechanism combining a channel-like selectivity filter in KdpA with the ATP-driven transport functionality of KdpB. A key unresolved question is whether K+ ions translocate through the inter-subunit tunnel as a queue of ions or individually within a hydrated environment. Using molecular dynamics simulations, metadynamics, anomalous X-ray scattering, and biochemical assays, we demonstrate that the tunnel is predominantly occupied by water molecules rather than multiple K+ ions. Our results identify only one stable intermediate binding site for K+ within the tunnel, apart from the canonical sites in KdpA and KdpB. Free energy c

SUBMITTER: Valia Madapally H 

PROVIDER: S-EPMC12833782 | biostudies-literature | 2026 Jan

REPOSITORIES: biostudies-literature