DOE Pulse
  • Number 306  |
  • March 1, 2010

How life’s smallest motor powers cellular engines

RHIC's quark-gluon plasma

Kinesin is one of life's smallest
molecular motors.

Inside cells, kinesin is the little engine that could, a protein that shuttles cargo within cells and helps cells divide. Microtubules are tube-shaped structures that form a cell’s skeleton; fueled by energy-giving ATP, a kinesin protein motors along a microtubule like a train on a railroad track.

Research by scientists at DOE’s Lawrence Berkeley National Laboratory reveals that the diminutive protein moves by rocking up and down like a seesaw. Biophysicist Ken Downing and his graduate student Charles Sindelar, now at Brandeis University, made the first-ever high-resolution snapshots of the kinesin motor as it walked along a microtubule, the closest look yet at the structural changes kinesin proteins undergo as they ferry molecules within cells.

Although x-ray crystallography of kinesin has enabled researchers to piece together the protein’s three-dimensional structure, those images don’t reveal how kinesin works as a motor. Downing and Sindelar used cryoelectron microscopy instead, imaging the proteins more as they would appear in real-world conditions.

“It is not until the protein motor binds to a microtubule that structural rearrangements occur that enable ATP hydrolysis, the process that transfers energy from ATP to kinesin,” says Downing. “We see for the first time how kinesin’s atomic-scale moving parts allow it to pull itself and its cargo along a microtubule.”

The researchers found that the pivot point where the kinesin motor attaches to the microtubule acts like a fulcrum and causes kinesin to rock up and down like a seesaw as it moves along. The seesaw motion is a key insight into one of life’s most fundamental processes.

The research is reported in the Proceedings of the National Academy of Sciences.

[Dan Krotz, 510.486.4019,]