189. SINGLE-MOLECULE INVESTIGATION AND MOLECULAR MODELING OF THE BACTERIOPHAGE T4 GENOME PACKAGING MOTOR

Department: NanoEngineering
Faculty Advisor(s): Gaurav Arya | Doug Smith

Primary Student
Name: Amy L Davenport
Email: adavenpo@ucsd.edu
Phone: 339-234-0603
Grad Year: 2012

Abstract
Bacteriophage T4 employs a molecular motor to package its genome during viral assembly. This motor has been shown to package at very high forces (>60N) and rates of speed (>2000bp/s), although the speed is unusually variable. We employ a dual optical tweezer setup to measure the dynamics of packaging of single DNA molecules by single T4 motor complexes. A structural model for motor function has been proposed based on cryo-EM and X-ray crystallographic data that allows us to probe the structure of the motor protein to identify particularly important regions. Key regions in this model include an interface between two globular subdomains with ion pairs proposed to help generate motor forces and a hinge region that allows for the subdomains to undergo ratchet-like motions. We describe measurements with mutant T4 terminase complexes having alterations in these regions that alter motor velocity and/or force generation capabilities. We also describe molecular modeling of the motor to provide insights into the catalytic mechanism and energetics of this motor protein. By combining our experimental data with simulation data, we hope to explain how the dynamic characteristics of this motor protein can be related to its structure.

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