Biology subjects

Reinemann, D. N.

Publications and source records attributed to Reinemann, D. N..

3 recordsLinked to original sources

bioRxiv2026

Tubulin E-hook Hexamers Reveal Charge Dependent Compaction and Transient Secondary Structure Signatures

This present work shows that E-hook fragments possess functional structure differences governed by electrostatic interactions and sequence composition. The acidic C-terminal tails of tubulin, known as E-hooks, play a central role in regulating interactions between microtubules and motor proteins, microtubule-associated proteins, and enzymatic modifiers. Despite their functional importance, the intrinsic structural properties of these peptide segments remain poorly characterized due to their intrinsically disordered nature. In this work, we present quantum-mechanically optimized structures of hexamer peptides derived from {beta}-tubulin E-hook sequences. Density functional theory calculations were used to optimize peptide geometries using progressively larger basis sets. From the optimized geometries we calculated theoretical Raman spectra, Ramachandran backbone dihedral distributions, and measured radii of gyration to resolve composition dependent structural tendencies. The combined Raman and conformational analyses provide a systematic computational approach for comparing simulated and experimental Raman spectra of tubulin E-hooks and other intrinsically disordered proteins and offer insight into how E-hooks contribute to the recognition mechanisms underlying the tubulin code.

biochemistry↗

bioRxiv2026

Motor Occupancy Defines Emergent Mechanical States in Cardiac Myosin Ensembles

Myosin II generates force through the collective action of mechanically coupled motor ensembles, yet the mechanisms by which these ensembles sense changes in motor occupancy and coordinate force generation remain poorly understood. Ensemble force production may be governed by an optimal balance between effective motor occupancy and mechanical coordination rather than by motor number alone. We reconstituted cardiac myosin ensembles and systematically perturbed effective motor occupancy using the small-molecule drugs omecamtiv mecarbil (OM), which prolongs actomyosin interactions, and mavacamten (MAVA), which reduces the number of available force-generating myosin heads. Optical trapping measurements of full-length and S1 cardiac myosin ensembles revealed that force generation depended on both myosin concentration and pharmacological perturbation. Reducing myosin concentration increased force generation in the absence of drug, while OM and MAVA produced responses that varied with the initial occupancy state of the ensemble. Low concentrations of MAVA enhanced force generation under high motor occupancy but reduced force under low motor occupancy, whereas OM produced occupancy-dependent changes in both endpoint force and force dynamics. Force traces further revealed changes in the persistence and temporal coordination of force generation. These findings support a model in which cardiac myosin ensembles operate along an occupancy-coordination landscape, where maximal force generation is achieved at an intermediate level of effective motor occupancy. Our results illuminate how changes in motor occupancy are translated into coordinated ensemble mechanics and suggest that emergent mechanical feedback through the shared actin filament may enable ensembles to collectively sense and adapt to their mechanical state.

biophysics↗

bioRxiv2021

A kinesin-1 variant reveals motor-induced microtubule damage in cells

Kinesins drive the transport of cellular cargoes as they walk along microtubule tracks, however, recent work has suggested that the physical act of kinesins walking along microtubules can stress the microtubule lattice. Here, we describe a kinesin-1 KIF5C mutant with an increased ability to generate defects in the microtubule lattice as compared to the wild-type motor. Expression of the mutant motor in cultured cells resulted in microtubule breakage and fragmentation, suggesting that kinesin-1 variants with increased damage activity would have been selected against during evolution. The increased ability to damage microtubules is not due to the altered motility properties of the mutant motor as expression of the kinesin-3 motor KIF1A, which has similar single-motor motility properties, also caused increased microtubule pausing, bending, and buckling but not breakage. In cells, motor-induced microtubule breakage could not be prevented by increased a-tubulin K40 acetylation, a post-translational modification known to increase microtubule flexibility. In vitro, lattice damage induced by wild-type KIF5C was repaired by soluble tubulin and resulted in increased rescues and microtubule growth whereas lattice damage induced by the KIF5C mutant resulted in larger repair sites that made the microtubule vulnerable to breakage and fragmentation when under mechanical stress. These results demonstrate that kinesin-1 motility causes defects in and damage to the microtubule lattice in cells. While cells have the capacity to repair lattice damage, conditions that exceed this capacity result in microtubule breakage and fragmentation and may contribute to human disease.

cell biology↗