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Somasundaran SM, Kompella SVK, Madapally HV, Vishnu EK, Balasubramanian S, Thomas KG. Red Circularly Polarized Luminescence from Dimeric H-Aggregates of Acridine Orange by Chiral Induction. J Phys Chem Lett 2024; 15:507-513. [PMID: 38190655 DOI: 10.1021/acs.jpclett.3c03127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
Understanding the mechanism of chirality transfer from a chiral surface to an achiral molecule is essential for designing molecular systems with tunable chiroptical properties. These aspects are explored herein using l- and d-isomers of alkyl valine amphiphiles, which self-assemble in water as nanofibers possessing a negative surface charge. An achiral chromophore, acridine orange, upon electrostatic binding on these surfaces displays mirror-imaged bisignated circular dichroism and red-emitting circularly polarized luminescence signals with a high dissymmetry factor. Experimental and computational investigations establish that the chiroptical properties emerge from surface-bound asymmetric H-type dimers of acridine orange, further supported by fluorescence lifetime imaging studies. Specifically, atomistic molecular dynamics simulations show that the experimentally observed chiral signatures have their origin in van der Waals interactions between acridine orange dimers and the amphiphile head groups as well as in the extent of solvent exposure of the chromophore.
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Affiliation(s)
- Sanoop Mambully Somasundaran
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Vithura, Thiruvananthapuram 695551, India
| | - Srinath V K Kompella
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur, Bangalore 560064, India
| | - Hridya Valia Madapally
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Vithura, Thiruvananthapuram 695551, India
| | - E Krishnan Vishnu
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Vithura, Thiruvananthapuram 695551, India
| | - Sundaram Balasubramanian
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur, Bangalore 560064, India
| | - K George Thomas
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Vithura, Thiruvananthapuram 695551, India
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Madapally HV, Abe K, Dubey V, Khandelia H. Specific protonation of acidic residues confers K + selectivity to the gastric proton pump. J Biol Chem 2024; 300:105542. [PMID: 38072058 PMCID: PMC10825007 DOI: 10.1016/j.jbc.2023.105542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Revised: 11/20/2023] [Accepted: 11/29/2023] [Indexed: 01/11/2024] Open
Abstract
The gastric proton pump (H+,K+-ATPase) transports a proton into the stomach lumen for every K+ ion exchanged in the opposite direction. In the lumen-facing state of the pump (E2), the pump selectively binds K+ despite the presence of a 10-fold higher concentration of Na+. The molecular basis for the ion selectivity of the pump is unknown. Using molecular dynamics simulations, free energy calculations, and Na+ and K+-dependent ATPase activity assays, we demonstrate that the K+ selectivity of the pump depends upon the simultaneous protonation of the acidic residues E343 and E795 in the ion-binding site. We also show that when E936 is protonated, the pump becomes Na+ sensitive. The protonation-mimetic mutant E936Q exhibits weak Na+-activated ATPase activity. A 2.5-Å resolution cryo-EM structure of the E936Q mutant in the K+-occluded E2-Pi form shows, however, no significant structural difference compared with wildtype except less-than-ideal coordination of K+ in the mutant. The selectivity toward a specific ion correlates with a more rigid and less fluctuating ion-binding site. Despite being exposed to a pH of 1, the fundamental principle driving the K+ ion selectivity of H+,K+-ATPase is similar to that of Na+,K+-ATPase: the ionization states of the acidic residues in the ion-binding sites determine ion selectivity. Unlike the Na+,K+-ATPase, however, protonation of an ion-binding glutamate residue (E936) confers Na+ sensitivity.
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Affiliation(s)
- Hridya Valia Madapally
- PHYLIFE, Physical Life Science, Department of Physics Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark
| | - Kazuhiro Abe
- Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Japan; Cellular and Structural Physiology Institute, Nagoya University, Nagoya, Japan
| | - Vikas Dubey
- PHYLIFE, Physical Life Science, Department of Physics Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark
| | - Himanshu Khandelia
- PHYLIFE, Physical Life Science, Department of Physics Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark.
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Tanaka S, Morita M, Yamagishi T, Madapally HV, Hayashida K, Khandelia H, Gerle C, Shigematsu H, Oshima A, Abe K. Structural Basis for Binding of Potassium-Competitive Acid Blockers to the Gastric Proton Pump. J Med Chem 2022; 65:7843-7853. [PMID: 35604136 DOI: 10.1021/acs.jmedchem.2c00338] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
As specific inhibitors of the gastric proton pump, responsible for gastric acidification, K+-competitive acid blockers (P-CABs) have recently been utilized in the clinical treatment of gastric acid-related diseases in Asia. However, as these compounds have been developed based on phenotypic screening, their detailed binding poses are unknown. We show crystal and cryo-EM structures of the gastric proton pump in complex with four different P-CABs, tegoprazan, soraprazan, PF-03716556 and revaprazan, at resolutions reaching 2.8 Å. The structures describe molecular details of their interactions and are supported by functional analyses of mutations and molecular dynamics simulations. We reveal that revaprazan has a novel binding mode in which its tetrahydroisoquinoline moiety binds deep in the cation transport conduit. The mechanism of action of these P-CABs can now be evaluated at the molecular level, which will facilitate the rational development and improvement of currently available P-CABs to provide better treatment of acid-related gastrointestinal diseases.
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Affiliation(s)
- Saki Tanaka
- Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, 464-8601, Japan
| | - Mikio Morita
- Discovery Research, RaQualia Pharma Inc., 1-21-19 Meieki Minami, Nakamura, Nagoya 450-0003, Japan.,RaQualia Pharma Industry-Academia Collaborative Research Center, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan
| | - Tatsuya Yamagishi
- Discovery Research, RaQualia Pharma Inc., 1-21-19 Meieki Minami, Nakamura, Nagoya 450-0003, Japan.,RaQualia Pharma Industry-Academia Collaborative Research Center, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan
| | - Hridya Valia Madapally
- PHYLIFE: Physical Life Science, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Kenichi Hayashida
- Cellular and Structural Physiology Institute, Nagoya University, Nagoya, 464-8601, Japan
| | - Himanshu Khandelia
- PHYLIFE: Physical Life Science, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Christoph Gerle
- RIKEN SPring-8 Center, Kouto, Sayo-gun, Hyogo 679-5148, Japan.,Laboratory for Protein Crystallography, Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | | | - Atsunori Oshima
- Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, 464-8601, Japan.,Cellular and Structural Physiology Institute, Nagoya University, Nagoya, 464-8601, Japan.,Institute for Glyco-core Research (iGCORE), Nagoya University, Nagoya, 464-8601, Japan
| | - Kazuhiro Abe
- Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, 464-8601, Japan.,Cellular and Structural Physiology Institute, Nagoya University, Nagoya, 464-8601, Japan
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