Biology subjects

Marcoline, F. V.

Publications and source records attributed to Marcoline, F. V..

2 recordsLinked to original sources

bioRxiv2026

Conformational changes upon pore blocker removal reveal conductive states of TMEM16A

TMEM16A is a Ca2+-activated anion channel that provides direct electrical feedback to the plasma membrane in response to intracellular Ca2+. Its conductive state remains unresolved, leaving questions about gating, Cl- permeation, and modulation by Ca2+, depolarization, and lipids. To investigate the open state, we performed molecular dynamics simulations of TMEM16A bound to the putative open-state blocker 1PBC. After inhibitor removal, the putative, pore-lining helix TM4 developed kinks at two sites: an upper site that opens the pore for Cl- permeation, and a deeper site causing constriction. A conserved hydrophobic network between TM3 and TM4 persisted in most open structures but separated during extreme dilation, allowing lipids to transiently block the pore. Patch-clamp recordings indicated that the intact network promotes activation. Further simulations yielded >60 Cl- permeation events and a single-channel conductance matching experiments. Additional electrostatic and kinetic modeling indicated that TMEM16As transition from outward-rectification to Ohmic conductance with increasing Ca2+ results from a weak voltage dependence of Ca2+ binding, which act cooperatively to open the pore. HIGHLIGHTSO_LIRemoval of the inhibitor 1PBC from TMEM16A induces spontaneous transitions to ion conductive and non-conductive states via bending in TM4 at two different locations. C_LIO_LISimulations suggest that the open state is stabilized by a small hydrophobic network between TM3 and 4 and disrupting this network biases channel closure in electrophysiological recordings. C_LIO_LIA kinetic model of conduction based on energetics from the all-atom MD simulations coupled to continuum calculations gives a linear current-voltage curve consistent with the fully open conformation and removal of 1 Ca2+ switches to an outwardly rectifying state via electrostatic influence on the Cl- energy profile. However, the rectification is too weak to match experiment, but a cooperative model of Ca2+ binding with weak voltage-dependence does match experiment. C_LI

biophysics↗

bioRxiv2022

Membrane curvature sensing and symmetry breaking of the M2 proton channel from Influenza A

The M2 proton channel aids in the exit of mature influenza viral particles from the host plasma membrane through its ability to stabilize regions of high negative gaussian curvature (NGC) that occur at the neck of budding virions. The channels are homo-tetramers that contain a cytoplasm-facing amphipathic helix (AH) that is necessary and sufficient for NGC generation; however, constructs containing the transmembrane spanning helix, which facilitates tetramerization, exhibit enhanced curvature generation. Here we used all-atom molecular dynamics (MD) simulations to explore the conformational dynamics of M2 channels in lipid bilayers revealing that the AH is dynamic, quickly breaking the 4-fold symmetry observed in most structures. Next, we carried out MD simulations with the protein restrained in 4-fold and 2-fold symmetric conformations to determine the impact on the membrane shape. While each pattern was distinct, all configurations induced pronounced curvature in the outer leaflet with rather subtle lipid tilt, while conversely, the inner leaflets adjacent to the AHs showed minimal curvature and significant lipid tilt. The MD-generated profiles at the protein-membrane interface were then extracted and used as boundary conditions in a continuum elastic membrane model to calculate the membrane bending energy of each conformation embedded in different membrane surfaces characteristic of a budding virus. The calculations show that all three M2 conformations are stabilized in concave spherical caps and destabilized in convex spherical caps, the latter reminiscent of a budding virus. Only C2-broken symmetry conformations are stabilized in NGC surfaces, by 1-3 kBT depending on the AH domain arrangement. The most favored conformation is stabilized in saddles with curvatures corresponding to 33 nm radii. In total, our work provides atomistic insight into the curvature sensing capabilities of M2 channels and how enrichment in the nascent viral particle depends on protein shape and membrane geometry.

biophysics↗