Biomolecular motors are remarkable molecular machines that directly convert chemical energy into movement. Yet the essential mechanisms remain unclear, making it difficult to customize them for versatile applications. In this paper, we present an example of a novel DNA motor that moves on DNA nanostructures by combining dynein and DNA-binding proteins.
Kinesin-1, a molecular motor that transports intracellular vesicles, has been proposed to achieve efficient unidirectional movements, by utilizing thermal fluctuations. However, our previous study revealed that kinesin was less efficient than expected, by measuring the work/dissipation during their motion in vitro. We thus hypothesized that kinesin is optimized for the intracellular environment, rather than for in vitro experimental conditions. This review briefly describes the difference between in vitro and in cells, focusing on nonthermal fluctuations that occur in living cells. We then introduce our recent findings that kinesin moves faster under external force fluctuations that mimic the intracellular environment.
It has been predicted that the fastest myosin in the biological world exists in alga Chara, but its identity has remained unknown. Recently, we succeeded in cloning the fastest myosin and characterized its amino acid sequence. We also we succeeded in solving the first atomic structure (2.8 Å resolution) of myosin 11, the fastest myosin class, using X-ray crystallography. Based on this crystal structure and mutation experiments, it appears that that the actin-binding region contributes to the fast movement of Chara myosin 11.
Gap junction channels and ATP release channels are called “large pore channels” because these have pore sizes that allow the permeation of various sizes of solutes, from ions to metabolites. We investigated the structures of C. elegans innexin-6 gap junction channels and human pannexin-1 channels with cryo-EM. Using nanodisc reconstitution, we found double-layer densities in the pore and lipid acyl chains in the intersubunit spaces. Together with the molecular dynamics simulation, these studies suggest a lipid gating mechanism for large pore channels in that phospholipids are diffused to the pore for channel closure.