Spring 2005 Physics Colloquium

February 9; Wednesday, PAS 220, 3pm

Omar Saleh
Ecole Normale Superieure

Single-molecule measurements of the motor protein FtsK

Motor proteins are energy-consuming enzymes that generate a physical motion in order to accomplish a biological task. FtsK is a bacterial motor protein that acts as a DNA pump: by translocating DNA, it moves newly-replicated bacterial chromosomes to their proper positions just before cell division. In order to understand this process, we have performed a series of experiments in which we detect the activity of a single FtsK motor as it interacts with a single stretched DNA molecule. Because we use a magnetic technique to manipulate the DNA molecule, we can sense both FtsK's linear motion, such as its velocity and the distances it travels, and its rotational motion: due to DNA's helical structure, most DNA-based motor proteins rotate as they move linearly. We have found that FtsK is quite an exceptional motor: it translocates incredibly quickly, but rotates relatively slowly while doing so. I will discuss how FtsK's rotational behavior appears to be related to the topology of the bacterial chromosome, a hypothesis that indicates an evolutionary origin for FtsK's unique translocation characteristics.