Motor proteins: molecular mechanisms and roles in cellular processes

We study biological motor proteins in single-molecule experiments with the goal of understanding the physical principles of biological force generation in a multitude of active transport processes. Motor proteins are the ubiquitous nanometer-scale mechanical engines at the basis of many crucial processes of life. Examples are intracellular transport processes, cell division, cell locomotion, and in complex large scale assemblies also macroscopic motion, such as muscle contraction, or flagellar motion. The non-equilibrium dynamics of these specialized enzymes, usually embedded in a complex regulatory and functional environment, are the essence of their function.
Observing dynamic events on the scale of single protein molecules is a major experimental challenge. We use laser-based single-molecule fluorescence techniques in vitro and in vivo to measure dynamics parameters of the motors, such as stepping time, velocity, conformation, randomness of motion and processivity. Current topics of our interest are the mechanism of processivity of conventional kinesin (a motor protein involved in transport in nerve cells) and kinesin-like motor proteins that are involved in cell division, such as Eg5 and ncd. These latter motors are thought to play a role in mitotic spindle formation by cross linking microtubules. The exact mechanism of these motors and their cooperativity is a key focus of our current experiments. In addition, we are starting a new research line on "intraflagellar transport" in C. elegans neurosensory cilia. Here we try, using a combination of in vitro experiments on isolated motor proteins and single-molecule imaging of motors in whole nematodes, to unravel this transport processes involving three different motors. Special emphasis in this project is on the way multiple motors are mechanically coupled and influence each other's motility parameters.

Peterman1 
Kinesin motor proteins, with two different dye molecules attached, walking over a microtubule. Locally, the kinesins are excited with green laser light, while the emitted fluorescence is measured with single-photon sensitivity. At the bottom of the figure, four characterstic signals are shown of individual kinesins walking through the laser focus (intensity of the light emitted by each of the dyes as a function of time).


Contact: Erwin Peterman, e-mail: EJG.Peterman@few.vu.nl