scholarly journals Acid activation mechanism of the influenza A M2 proton channel

2016 ◽  
Vol 113 (45) ◽  
pp. E6955-E6964 ◽  
Author(s):  
Ruibin Liang ◽  
Jessica M. J. Swanson ◽  
Jesper J. Madsen ◽  
Mei Hong ◽  
William F. DeGrado ◽  
...  
Keyword(s):  
Free Energy ◽  
Proton Transport ◽  
Influenza A ◽  
Conduction Mechanism ◽  
Transmembrane Domain ◽  
Proton Conduction ◽  
Proton Flux ◽  
Activation Mechanism ◽  
Proton Channel ◽  
Acid Activation

The homotetrameric influenza A M2 channel (AM2) is an acid-activated proton channel responsible for the acidification of the influenza virus interior, an important step in the viral lifecycle. Four histidine residues (His37) in the center of the channel act as a pH sensor and proton selectivity filter. Despite intense study, the pH-dependent activation mechanism of the AM2 channel has to date not been completely understood at a molecular level. Herein we have used multiscale computer simulations to characterize (with explicit proton transport free energy profiles and their associated calculated conductances) the activation mechanism of AM2. All proton transfer steps involved in proton diffusion through the channel, including the protonation/deprotonation of His37, are explicitly considered using classical, quantum, and reactive molecular dynamics methods. The asymmetry of the proton transport free energy profile under high-pH conditions qualitatively explains the rectification behavior of AM2 (i.e., why the inward proton flux is allowed when the pH is low in viral exterior and high in viral interior, but outward proton flux is prohibited when the pH gradient is reversed). Also, in agreement with electrophysiological results, our simulations indicate that the C-terminal amphipathic helix does not significantly change the proton conduction mechanism in the AM2 transmembrane domain; the four transmembrane helices flanking the channel lumen alone seem to determine the proton conduction mechanism.

scholarly journals From Acid Activation Mechanisms of Proton Conduction to Design of Inhibitors of the M2 Proton Channel of Influenza A Virus

2022 ◽  
Vol 8 ◽  
Author(s):  
Elnaz Aledavood ◽  
Beatrice Selmi ◽  
Carolina Estarellas ◽  
Matteo Masetti ◽  
F. Javier Luque
Keyword(s):  
Proton Transport ◽  
Influenza A ◽  
Viral Proteins ◽  
Fusion Peptide ◽  
Proton Channel ◽  
Acid Activation ◽  
Endosomal Membranes ◽  
Activation Mechanisms ◽  
Resistant Strains ◽  
M2 Proton Channel

With an estimated 1 billion people affected across the globe, influenza is one of the most serious health concerns worldwide. Therapeutic treatments have encompassed a number of key functional viral proteins, mainly focused on the M2 proton channel and neuraminidase. This review highlights the efforts spent in targeting the M2 proton channel, which mediates the proton transport toward the interior of the viral particle as a preliminary step leading to the release of the fusion peptide in hemagglutinin and the fusion of the viral and endosomal membranes. Besides the structural and mechanistic aspects of the M2 proton channel, attention is paid to the challenges posed by the development of efficient small molecule inhibitors and the evolution toward novel ligands and scaffolds motivated by the emergence of resistant strains.

scholarly journals Acid-Activation, Proton Transport Rate Saturation, and pH-Dependence of Amantadine Block for Influenza a M2 Protein Truncate (22-62)

2010 ◽  
Vol 98 (3) ◽  
pp. 503a ◽  
Author(s):  
Emily Peterson ◽  
Myunggi Yi ◽  
Huan-Xiang Zhou ◽  
Mukesh Sharma ◽  
Timothy A. Cross ◽  
...  
Keyword(s):  
Proton Transport ◽  
Influenza A ◽  
Ph Dependence ◽  
Transport Rate ◽  
Acid Activation ◽  
M2 Protein

scholarly journals pH Titration and Acid Activation of the Full-Length Influenza a M2 Proton Channel in Lipid Bilayers

2015 ◽  
Vol 108 (2) ◽  
pp. 246a
Author(s):  
Yimin Miao ◽  
Riqiang Fu ◽  
Huan-Xiang Zhou ◽  
Huajun Qin ◽  
Timothy A. Cross
Keyword(s):  
Lipid Bilayers ◽  
Influenza A ◽  
Full Length ◽  
Proton Channel ◽  
Acid Activation ◽  
Ph Titration ◽  
M2 Proton Channel

Interpreting Thermodynamic Profiles of Aminoadamantane Compounds Inhibiting the M2 Proton Channel of Influenza A by Free Energy Calculations

2016 ◽  
Vol 56 (1) ◽  
pp. 110-126 ◽  
Author(s):  
Nadine Homeyer ◽  
Harris Ioannidis ◽  
Felix Kolarov ◽  
Günter Gauglitz ◽  
Christos Zikos ◽  
...  
Keyword(s):  
Free Energy ◽  
Influenza A ◽  
Free Energy Calculations ◽  
Proton Channel ◽  
Energy Calculations ◽  
M2 Proton Channel

scholarly journals Effect of Cytoplasmic Tail Truncations on the Activity of the M2 Ion Channel of Influenza A Virus

1999 ◽  
Vol 73 (12) ◽  
pp. 9695-9701 ◽  
Author(s):  
Kurt Tobler ◽  
Marie L. Kelly ◽  
Lawrence H. Pinto ◽  
Robert A. Lamb
Keyword(s):  
Ion Channel ◽  
Influenza A Virus ◽  
Influenza A ◽  
Transmembrane Domain ◽  
Stop Codon ◽  
Specific Inhibitor ◽  
Cytoplasmic Tail ◽  
Proton Channel ◽  
Tail Region

ABSTRACT The M2 protein of influenza A virus forms a proton channel that is required for viral replication. The M2 ion channel is a homotetramer and has a 24-residue N-terminal extracellular domain, a 19-residue transmembrane domain, and a 54-residue cytoplasmic tail. We show here that the N-terminal methionine residue is cleaved from the mature protein. Translational stop codons were introduced into the M2 cDNA at residues 46, 52, 62, 72, 77, 82, 87, and 92. The deletion mutants were designated truncx, according to the amino acid position that was changed to a stop codon. We studied the role of the cytoplasmic tail by measuring the ion channel activity (the current sensitive to the M2-specific inhibitor amantadine) of the cytoplasmic tail truncation mutants expressed in oocytes of Xenopus laevis. When their conductance was measured over time, mutants trunc72, trunc77, and trunc92 behaved comparably to wild-type M2 protein (a decrease of only 4% over 30 min). In contrast, conductance decreased by 28% for trunc82, 27% for trunc62, and 81% for trunc52 channels. Complete closure of the channel could be observed in some cells for trunc62 and trunc52 within 30 min. These data suggest that a role of the cytoplasmic tail region of the M2 ion channel is to stabilize the pore against premature closure while the ectodomain is exposed to low pH.

scholarly journals Molecular basis of inhibition and resistance of the influenza M2 ion channel by aminoadamantane drugs and discovery of nomel resistance - breaking inhibitors targeting the mutant M2 proton channel

2018 ◽  
Author(s):  
Χριστίνα Τζιτζογλάκη
Keyword(s):  
Solid State ◽  
Ion Channel ◽  
Solid State Nmr ◽  
Molecular Basis ◽  
Influenza A ◽  
Transmembrane Domain ◽  
Proton Channel ◽  
Resistance Breaking ◽  
M2 Proton Channel

Η αμανταδίνη (Amt ) και η ριμανταδίνη (Rim) είναι αναστολείς της μεταφοράς πρωτονίων διαμέσου του ιοντικού διαύλου της πρωτεΐνης Μ2 του ιού influenza A, και αποτέλεσαν εγκεκριμένα μέσα πρόληψης και θεραπείας έναντι των ιών της γρίπης Α άγριου τύπου (WT). Ωστόσο, από το 2005, η μετάλλαξη του αμινοξέος σερίνη σε ασπαραγίνη στη θέση 31 (S31N) στην Μ2 πρωτεΐνη, δημιούργησε ένα στέλεχος ανθεκτικό στην Amt το οποίο έχει κυριαρχήσει παγκοσμίως, καταργώντας την κλινική χρησιμότητα της αμανταδίνης και πιθανότατα και άλλων προαναφερθέντων, στη διεθνή βιβλιογραφία, αναστολέων της Μ2. Επομένως, είναι απαραίτητη η ανάπτυξη νέων μορίων για την καταπολέμηση των ανθεκτικών στελεχών της γρίπης. H κύρια θέση πρόσδεσης της Amt (1) και της Rim (2) είναι η διαμεμβρανική περιοχή (transmembrane domain, TM) των αμινοξέων 22-46 του συμπλέγματος των τεσσάρων α-ελίκων της Μ2 που σχηματίζει τον δίαυλο μεταφοράς πρωτονίων. Σύμφωνα με δομές υψηλής διαχωριστικότητας που προέκυψαν από πειράματα κρυσταλλογραφίας ακτίνων-Χ και φασματοσκοπίας πυρηνικού μαγνητικού συντονισμού στερεάς κατάστασης (solid state NMR, ssNMR) και δημοσιεύτηκαν μεταξύ 2008-2011 από τους ερευνητές και καθηγητές Tim Cross, William DeGrado και Mei Hong στα πιο έγκριτα περιοδικά όπως Nature, JACS κλπ, η Amt (1) και η Rim (2) δρουν φράσσοντας τον πόρο του διαύλου M2TM. Ο κλωβός του αδαμαντανίου των ενώσεων αυτών περικλείεται από τις τέσσερεις πλευρικές αλυσίδες των V27 και της A30 του τετραμερούς M2TM προκαλώντας τον στερεοχημικό αποκλεισμό της μεταφοράς πρωτονίων και αποτρέποντας την συνέχεια του κύκλου ζωής του ιού. Τα αποτελέσματα ssNMR έδειξαν επίσης ότι η ομάδα αμμωνίου αυτών των φαρμάκων έχει προσανατολισμό προς τα τέσσερα αμινοξέα της His37 δηλαδή προς το C-τελικό άκρο.9 Αυτός ο προσανατολισμός σταθεροποιείται μέσω ενός δικτύου δεσμών υδρογόνου μεταξύ προσδέτη και (α) μορίων νερού εντός του πόρου του ιοντικού διαύλου, που βρίσκονται μεταξύ ιμιδαζολίου της H37 και προσδέτη, και, ενδεχομένως, (β) με το καρβονύλιο της A30 σύμφωνα με πειραματικά αποτελέσματα και προσομοιώσεις μοριακής δυναμικής (MD).Δεδομένου ότι η M2TM αποτελεί το απλούστερο μοντέλο πρόσδεσης της Amt (1) και Rim (2) για την M2, οι προηγούμενες πειραματικές δομές υψηλής ανάλυσης μπορούν να χρησιμοποιηθούν για το σχεδιασμό και ανάπτυξη νέων αναστολέων που να συνδέονται αποτελεσματικότερα με τον πόρο Μ2ΤΜ, μέσω προσομοιώσεων μοριακής δυναμικής (MD) 19ή ακριβέστερα με υπολογισμούς ελεύθερης ενέργειας.

A Robust Proton Flux (pHlux) Assay for Studying the Function and Inhibition of the Influenza A M2 Proton Channel

Biochemistry ◽  
2018 ◽  
Vol 57 (41) ◽  
pp. 5949-5956 ◽  
Author(s):  
Paul Santner ◽  
João Miguel da Silva Martins ◽  
Jonas S. Laursen ◽  
Lars Behrendt ◽  
Leise Riber ◽  
...  
Keyword(s):  
Influenza A ◽  
Proton Flux ◽  
Proton Channel ◽  
M2 Proton Channel

scholarly journals Multiscale Simulation of an Influenza A M2 Channel Mutant Reveals Key Features of Its Markedly Different Proton Transport Behavior

2021 ◽  
Author(s):  
Laura C. Watkins ◽  
William F. DeGrado ◽  
Gregory A. Voth
Keyword(s):  
Free Energy ◽  
Proton Transport ◽  
Influenza A ◽  
Water Structure ◽  
Multiscale Simulation ◽  
Reactive Molecular Dynamics ◽  
Activated State ◽  
Ph Range ◽  
And Shifts

ABSTRACTThe influenza A M2 channel, a prototype for the viroporin class of viral channels, is an acid-activated viroporin that conducts protons across the viral membrane, a critical step in the viral life cycle. As the protons enter from the viral exterior, four central His37 residues control the channel activation by binding subsequent protons, which opens the Trp41 gate and allows proton flux to the viral interior. Asp44 is essential for maintaining the Trp41 gate in a closed state at high pH, which results in asymmetric conduction. The prevalent D44N mutant disrupts this gate and opens the C-terminal end of the channel, resulting in overall increased conduction in the physiologically relevant pH range and a loss of this asymmetric conduction. Here, we use extensive Multiscale Reactive Molecular Dynamics (MS-RMD) and Quantum Mechanics/Molecular mechanics (QM/MM) simulations with an explicit, reactive excess proton to calculate the free energy of proton transport in the M2 mutant and to study the dynamic molecular-level behavior of D44N M2. We find that this mutation significantly lowers the barrier of His37 deprotonation in the activated state and shifts the barrier for entry up to the Val27 tetrad. These free energy changes are reflected in structural shifts. Additionally, we show that the increased hydration around the His37 tetrad diminishes the effect of the His37 charge on the channel’s water structure, facilitating proton transport and enabling activation from the viral interior. Altogether, this work provides key insight into the fundamental characteristics of PT in WT M2 and how the D44N mutation alters this PT mechanism, and it expands our understanding of the role of emergent mutations in viroporins.

scholarly journals High-resolution structures of the M2 channel from influenza A virus reveal dynamic pathways for proton stabilization and transduction

2015 ◽  
Vol 112 (46) ◽  
pp. 14260-14265 ◽  
Author(s):  
Jessica L. Thomaston ◽  
Mercedes Alfonso-Prieto ◽  
Rahel A. Woldeyes ◽  
James S. Fraser ◽  
Michael L. Klein ◽  
...  
Keyword(s):  
High Resolution ◽  
Influenza A Virus ◽  
Influenza A ◽  
Transmembrane Domain ◽  
Proton Channel ◽  
The Matrix ◽  
Crystallographic Structures ◽  
Decreasing Ph ◽  
Dynamics Simulations ◽  
Increasing Temperature

The matrix 2 (M2) protein from influenza A virus is a proton channel that uses His37 as a selectivity filter. Here we report high-resolution (1.10 Å) cryogenic crystallographic structures of the transmembrane domain of M2 at low and high pH. These structures reveal that waters within the pore form hydrogen-bonded networks or “water wires” spanning 17 Å from the channel entrance to His37. Pore-lining carbonyl groups are well situated to stabilize hydronium via second-shell interactions involving bridging water molecules. In addition, room temperature crystallographic structures indicate that water becomes increasingly fluid with increasing temperature and decreasing pH, despite the higher electrostatic field. Complementary molecular dynamics simulations reveal a collective switch of hydrogen bond orientations that can contribute to the directionality of proton flux as His37 is dynamically protonated and deprotonated in the conduction cycle.

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