The vacuolar H-ATPase (V-ATPase; VV-ATPase) is an ATP-dependent proton pump that acidifies subcellular compartments in all eukaryotic organisms. V-ATPase activity is regulated by reversible disassembly into autoinhibited V-ATPase and V proton channel subcomplexes, a process that is poorly understood on the molecular level. V-ATPase is a rotary motor, and recent structural analyses have revealed different rotary states for disassembled V and V, a mismatch that is likely responsible for their inability to reconstitute into holo V-ATPase Here, using the model organism , we show that a key impediment for binding of V to V is the conformation of the inhibitory C-terminal domain of subunit H (H). Using biolayer interferometry and biochemical analyses of purified mutant V-ATPase and V proton channel reconstituted into vacuolar lipid-containing nanodiscs, we further demonstrate that disruption of H's V-binding site facilitates assembly of a functionally coupled and stable VV-ATPase. Unlike WT, this mutant enzyme was resistant to MgATP hydrolysis-induced dissociation, further highlighting H's role in the mechanism of V-ATPase regulation. Our findings provide key insight into the molecular events underlying regulation of V-ATPase activity by reversible disassembly.
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http://dx.doi.org/10.1074/jbc.RA119.007577 | DOI Listing |
Proc Natl Acad Sci U S A
February 2025
Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena 07740, Germany.
In mammals, the four subunit isoforms HCN1-4 assemble to form functional homotetrameric and heterotetrameric hyperpolarization-activated cyclic nucleotide-modulated (HCN) ion channels. Despite the outstanding relevance of HCN channels for organisms, including generating electrical rhythmicity in cardiac pacemaker cells and diverse types of brain neurons, key channel properties are still elusive. In particular, the unitary conductance, of HCN channels is highly controversial.
View Article and Find Full Text PDFACS Appl Mater Interfaces
January 2025
State Key Laboratory of Advanced Chemical Power Sources (Chongqing University), Chongqing 400044, China.
Investigating how the size of carbon support pores influences the three-phase interface of platinum (Pt) particles in fuel cells is essential for enhancing catalyst utilization. This study employed molecular dynamics simulations and density functional theory calculation to examine the effects of mesoporous carbon support size, specifically its pore diameter, on Nafion ionomer distribution, as well as on proton and gas/liquid transport channels, and the utilization of Pt active sites. The findings show that when Pt particles are located within the pores of carbon support (Pt/PC), there is a significant enhancement in the spatial distribution of Nafion ionomer, along with a reduction in encapsulation around the Pt particles, compared to when Pt particles are positioned on the surface or in excessively large pores of the carbon support.
View Article and Find Full Text PDFMagn Reson Med
January 2025
Department 8.1 - Biomedical Magnetic Resonance, Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.
Purpose: To develop a low-cost, high-performance, versatile, open-source console for low-field MRI applications that can integrate a multitude of different auxiliary sensors.
Methods: A new MR console was realized with four transmission and eight reception channels. The interface cards for signal transmission and reception are installed in PCI Express slots, allowing console integration in a commercial PC rack.
ACS Phys Chem Au
January 2025
School of Science, Constructor University, Campus Ring 1, 28759 Bremen, Germany.
Many important processes in cells depend on the transfer of protons through water wires embedded in transmembrane proteins. Herein, we have performed more than 55 μs all-atom simulations of the light-harvesting complex of a diatom, i.e.
View Article and Find Full Text PDFJ Phys Chem Lett
January 2025
Department of Physics, City University of Hong Kong, Kowloon 999077, Hong Kong, China.
Amines are one of the most ubiquitous functional groups in molecular junctions; however, the exact regulation of the charge transport through the protonation state of an amine group in the junction backbone remains elusive. We address this question here by designing a diphenylamine molecular backbone and experimentally investigating how protonation of the central amine group affects the charge transport. Our ultraviolet-visible spectroscopy measurements demonstrate the protonation reaction of the diphenylamine compound in the presence of either trifluoroacetic acid or HCl, and we observe a consistent trend of a modestly increased conductance for diphenylamine in the presence of acid, indicating that a protonated amine group in a diphenylamine backbone slightly enhances the electron conduction.
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