Stokes, D. | bioRxiv Science

bioRxiv2025

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

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 within a hydrated environment. Using molecular dynamics (MD) 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 calculations reveal a substantial barrier ([~]22 kcal/mol) at the KdpA-KdpB interface, making spontaneous K+ translocation unlikely. Furthermore, mutagenesis and functional assays confirm previous findings that Phe232 at this interface plays a key role in coupling ATP hydrolysis to K+ transport. These findings challenge previous models proposing a continuous wire of K+ ions through the tunnel and suggest the existence of an as-yet unidentified intermediate state or mechanistic detail that facilitates K+ movement into KdpB.

biophysics↗

bioRxiv2022

Phylogenetic analyses reveal bat communities in Northwestern Mexico harbour a high diversity of novel cryptic ectoparasite species

BackgroundParasites are integral parts of ecosystem function and important drivers of evolutionary processes. Characterising ectoparasite diversity is fundamental to studies of host-parasite interactions, evolution, and conservation, and also for understanding emerging disease threats for some vector borne pathogens. With more than 1,400 species, bats represent the second most speciose mammalian clade, but their ectoparasite fauna are poorly known for most species. MethodsWe sequenced mitochondrial Cytochrome Oxidase C subunit I and nuclear 18S ribosomal gene fragments, and used Bayesian phylogenetic analyses to characterise ectoparasite taxon identity and diversity for 17 species of parasitized bats sampled along the Baja California peninsula and in Northwestern Mexico. ResultsThe sequence data revealed multiple novel lineages of bat bugs (Cimicidae), flies (Nycteribiidae and Streblidae) and ticks (Argasidae). Within families, the new linages showed more than 10% sequence divergence, which is consistent with separation at least at the species level. Both families of bat flies showed host specificity, particularly on Myotis species. We also identified new records for the Baja peninsula of one tick (Carios kelleyi), and of five Streblid bat flies. One Nycteribiid bat fly haplotype from Pallid bat (Antrozous pallidus) hosts was found throughout the peninsula, suggesting potential long distance co-dispersal with hosts. Different bat bug and tick communities were found in the north and south of the peninsula. ConclusionsThis study is the first systematic survey of bat ectoparasites in the Baja California peninsula, discovering highly genetically differentiated novel lineages compared to other parts of North America. For some ectoparasite species, haplotype distributions may reflect patterns of bat migration. This work is a first step in characterising ectoparasite diversity over the Baja California peninsula, and understanding how ecological and evolutionary interactions shape bat ectoparasite communities among host species in different parts of their ranges.

ecology↗