Transport efficiency of membrane-anchored kinesin-1 motors depends on motor density and diffusivity.
In eukaryotic cells, membranous vesicles and organelles are transported by ensembles of motor proteins. These motors, such as kinesin-1, have been well characterized in vitro as single molecules or as ensembles rigidly attached to nonbiological substrates. However, the collective transport by membrane-anchored motors, that is, motors attached to a fluid lipid bilayer, is poorly understood. Here, we investigate the influence of motors' anchorage to a lipid bilayer on the collective transport characteristics. We reconstituted "membrane-anchored" gliding motility assays using truncated kinesin-1 motors with a streptavidin-binding peptide tag that can attach to streptavidin-loaded, supported lipid bilayers. We found that the diffusing kinesin-1 motors propelled the microtubules in the presence of ATP. Notably, we found the gliding velocity of the microtubules to be strongly dependent on the number of motors and their diffusivity in the lipid bilayer. The microtubule gliding velocity increased with increasing motor density and membrane viscosity, reaching up to the stepping velocity of single motors. This finding is in contrast to conventional gliding motility assays where the density of surface-immobilized kinesin-1 motors does not influence the microtubule velocity over a wide range. We reason that the transport efficiency of membrane-anchored motors is reduced because of their slippage in the lipid bilayer, an effect that we directly observed using single-molecule fluorescence microscopy. Our results illustrate the importance of motor-cargo coupling, which potentially provides cells with an additional means of regulating the efficiency of cargo transport.
Center for Molecular Bioengineering (B CUBE), Technische Universität Dresden, 01069 Dresden, Germany.|Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.|Center for Advancing Electronics Dresden, Technische Universität Dresden, 01069 Dresden, Germany.
Rahul
R
Grover
Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
Janine
J
Fischer
Center for Molecular Bioengineering (B CUBE), Technische Universität Dresden, 01069 Dresden, Germany.|Center for Advancing Electronics Dresden, Technische Universität Dresden, 01069 Dresden, Germany.
Friedrich W
FW
Schwarz
Center for Molecular Bioengineering (B CUBE), Technische Universität Dresden, 01069 Dresden, Germany.
Wilhelm J
WJ
Walter
Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
Petra
P
Schwille
Center for Molecular Bioengineering (B CUBE), Technische Universität Dresden, 01069 Dresden, Germany; diez@bcube-dresden.de.|Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.|Center for Advancing Electronics Dresden, Technische Universität Dresden, 01069 Dresden, Germany.
Stefan
S
Diez
D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry; D016547:Kinesins / Q000737:chemistry / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D051381:Rats
D002352:Carrier Proteins; D008051:Lipid Bilayers; C452700:streptavidin-binding peptide; D016547:Kinesins
lipid bilayers; molecular motors; motor-cargo coupling; streptavidin-binding peptide; transport efficiency