Identifying Protein Association by Brightness Microscopy: From Principles to Retroviral Assembly

Who:  Joachim D. Mueller - (University of Minnesota)
Where:  1080 PRB, Robert Smith Seminar Room
When:  Wednesday, November 18, 2009 at 11:00
Type:  Biophysics Seminar

Description: A hallmark of biological systems is the assembly of proteins into complexes that perform specialized functions within the cell. But despite their pivotal role quantitative characterization of protein assemblies in cells remains a significant challenge. Fluorescence fluctuation spectroscopy offers a unique approach to study protein interactions directly inside living cells. The technique observes the transient signal of fluorescently labeled protein complexes passing through a small optical volume and determines their brightness, which is a measure of the fluorescence signal per complex. I will discuss the concept of brightness analysis and its usefulness in obtaining the stoichiometry and binding curve of protein complexes. We applied brightness microscopy to study the early stages of retroviral assembly and specifically investigate interactions of the Gag structural protein common to all retroviruses. Finally, we attempt a direct characterization of viral-like particles formed from human immunodeficiency virus type 1 Gag protein and determine the stoichiometry of Gag within the particles.

Additional Notes: Faculty Host: Michael Poirier