Professor John E. Johnson
Department of Molecular Biology
The Scripps Research Institute
La Jolla, CA

Monday, January 24, 2005
3:00 pm (CT)
3269 Beckman Institute

Abstract

Programmed movement at the molecular level is the essence of living systems. Virus maturation occupies an interesting and informative niche in the arena of large-scale molecular motion and associated driving forces. They require the formation of assembly intermediates due to the intricate and convoluted nature of the final nucleoprotein products. These intermediates organize a complete or partial inventory of particle components through an initial equilibrium reaction that favors assembly. At a defined stage of this process elements of the transitional complex (often a virally encoded protease or an electrostatic switch) are activated to create an irreversible assembly state that is, itself, metastable. This intermediate is referred to as a procapsid and normally matures shortly after assembly and does not accumulate unless maturation is blocked. The procapsids are imbued with an energy landscape that, when raised from the local minima, drives programmed subunit trajectories of exceptional length and rotary motion leading to dramatic changes in the contacts between subunits. The termination of this reorganization achieves a global energy minimum and a structure that defines the mature virion. We have investigated virus maturation for a ssRNA virus capsid and a dsDNA virus capsid both as ensembles and as single particles. Details of the structure and chemistry of these transitions will be presented and related to other molecular machines.

Tea and coffee will be served in R3151 Beckman Institute at 2:15pm.