The atomic-level action of a remarkable class of ring-shaped protein motors has been uncovered by researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) using a state-of-the-art protein crystallography beamline at the Advanced Light Source (ALS). These protein motors play pivotal roles in gene expression and replication, and are vital to the survival of all biological cells, as well as infectious agents, such as the human papillomavirus, which has been linked to cervical cancer.
James Berger, a biochemist and structural biologist who holds joint appointments with Berkeley Lab's Physical Biosciences Division and University of California Berkeley's Department of Molecular and Cell Biology, and Nathan Thomsen, a graduate student in his research group, have captured a critical action shapshot of an enzyme known as the Rho transcription termination factor. In bacteria, the Rho motor protein binds to a specific region of messenger RNA and translocates along the chain to selectively terminate transcription at discrete points along the genome.
"We have shown that the Escherichia coli Rho transcription termination factor functions like a rotary engine, much like the motors found on certain classes of propeller airplanes," says Berger. "As the motor spins, fueled by the chemical energy in ATP nucleotides, it pulls RNA strands through it's interior, an action that enables Rho to walk along RNA chains. Interestingly, the rotary firing order of the motor is biased so that the Rho protein can walk in only one direction along the RNA chain."
Berger and Thomsen are the co-authors of a paper reporting the results this research that has been published in the journal Cell. The paper is titled: "Running in reverse: the structural basis for translocation polarity in hexameric helicases."
The Rho factor is a member of the hexameric helicase superfamily of enzymes - ring-shaped proteins made up of six independent subunits
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory