Biophysical Society Conference | Tahoe 2024

Molecular Biophysics of Membranes

Tuesday Speaker Abstracts

DISTILLING COMPLEX PROTON CHANNELS INTO SIMPLE MODEL SYSTEMS THROUGH PROTEIN DESIGN Nolan Jacob 1 ; Vincent Silverman 1 ; Huong T. Kratochvil ; 1 University of North Carolina at Chapel Hill, Chemistry, Chapel Hill, NC, USA Proton channels and transporters move a precise and well-defined number of protons across cellular membranes to initiate bioenergetic and biocatalytic processes. Proton conduction pathways in these proteins are composed of hydrogen-bonded networks of water molecules and ionizable sidechains that enable the rapid movement of protons with minimal conformational rearrangement. Hydrophobic regions that are deceptively devoid of water also play a critical role in the selective transport of protons across the membrane. The short 8-12Å hydrophobic regions in proton channels and transporters prevent the translocation of other ions and allow for the formation of proton-conducive transient hydrogen-bonded water wires through these conduction pathways. In previous work, we used a combination of protein design, molecular dynamics (MD) simulations, crystallography, and functional liposomal assays to define proton conduction along these transient water wires in hydrophobic regions. Our designed channels, which incorporate polar Gln residues into hydrophobic pores, were proton-selective and able to move protons at rates seen in natural proton channels. We showed that the ability for these channels to form transient water wires is enough to enable proton-selective transport. Now, our lab is interested in the physicochemical nature of the sidechains in water wire formation and proton conduction rates. We have designed a new class of proton channels and are looking at how ionizable sidechains like His, Glu, and Asp affect the energetic barriers for water wire formation within these pores and how charge stabilization impacts conduction rates. Further, we also design new channels that increase the number of polar sidechains within the conduction pathway to address key questions about pore hydration and proton conduction rates. Our unique study enables us to distill complex natural channels into simple model systems, allowing us to pinpoint how different residues and hydration lengths affect proton channel selectivity and conductivity.

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