Potnuru, L. R. | bioRxiv Science

bioRxiv2025

Hydraulic Activation of the AsLOV2 photoreceptor

How proteins transduce light into mechanical energy remains a central question in biology. This study tests the hypothesis that blue light activation of the LOV2 (light, oxygen, voltage sensitive) domain of Avena sativa phototropin 1 (AsLOV2), gives rise to concerted water movement that induces protein conformational extensions. Using electron and nuclear magnetic resonance spectroscopy, along with molecular dynamics simulations at high pressure, we find AsLOV2 activation can be initiated by blue light or high pressure, followed by selective and concerted expulsion of low-entropy, tetrahedrally coordinated "wrap" water from the protein hydration shell. These findings suggest that interfacial water serves as constituents to reshape the proteins free energy landscape during activation. Our study highlights hydration water as an active hydraulic fluid that can drive long-range conformational changes underlying protein mechanics upon light activation and offers a new concept for engineering externally controllable protein actuators. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=70 SRC="FIGDIR/small/660617v2_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1a35f9dorg.highwire.dtl.DTLVardef@da4991org.highwire.dtl.DTLVardef@113e9b2org.highwire.dtl.DTLVardef@53d9fc_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2024

Phosphoryl group wires stabilize pathological tau fibrils as revealed by multiple quantum spin counting NMR

Hyperphosphorylation of the protein tau is one of the biomarkers of neurodegenerative diseases in the category of tauopathies. However, the molecular level, mechanistic, role of this common post- translational modification (PTM) in enhancing or reducing the aggregation propensity of tau is unclear, especially considering that combinatorial phosphorylation of multiple sites can have complex, non-additive, effects on tau protein aggregation. Since tau proteins stack in register and parallel to elongate into pathological fibrils, phosphoryl groups from adjacent tau strands with 4.8 [A] separation must find an energetically favorable spatial arrangement. At first glance, this appears to be an unfavorable configuration due to the proximity of negative charges between phosphate groups from adjacent neighboring tau fibrils. However, this study tests a counterhypothesis that phosphoryl groups within the fibril core-forming segments favorably assemble into highly ordered, hydrogen-bonded, one-dimensionally extended wires under biologically relevant conditions. We selected two phosphorylation sites associated with neurodegeneration, serine 305 (S305p) and tyrosine 310 (Y310p), on a model tau peptide jR2R3-P301L (tau295-313) spanning the R2/R3 splice junction of tau, that readily aggregate into a fibril with characteristics of a seed-competent mini prion. Using multiple quantum spin counting (MQ-SC) by 31P solid-state NMR of phosphorylated jR2R3-P301L tau peptide fibrils, enhanced by dynamic nuclear polarization, we find that at least six phosphorous spins must neatly arrange in 1D within fibrils or in 2D within a protofibril to yield the experimentally observed MQ-coherence orders of four. We found that S305p stabilizes the tau fibrils and leads to more seeding-competent fibrils compared to jR2R3 P301L or Y310p. This study introduces a new concept that phosphorylation of residues within a core forming tau segment can mechanically facilitate fibril registry and stability due a hitherto unrecognized role of phosphoryl groups to form highly ordered, extended, 1D wires that stabilize pathological tau fibrils. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=168 SRC="FIGDIR/small/606685v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@eb7176org.highwire.dtl.DTLVardef@1661a3forg.highwire.dtl.DTLVardef@4548dforg.highwire.dtl.DTLVardef@b353b2_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗