Speaker: John Ogren

When: April 26, 2012 (Thu), 10:00AM to 11:00AM (add to my calendar)

Location: SCI 352

Examining Committee:

Kenneth Rothschild (Advisor)

Shyamsunder Erramilli
Xue Han

Robert Carey

Claudio Chamon

 

Abstract:

Archaerhodopsin-3 (AR3) is a light driven proton pump found in Halorubrum Sodomese.  Recent studies have shown that AR3 and some of its mutants can be used both as effective genetically targetable neuronal silencers and as in vivo fluorescent sensors of membrane potential.  AR3 has a 73% sequence similarity with the more extensively studied bacteriorhodopsin (BR) proton pump from Halobacterium Halobium but unlike BR, very little is known about the details of AR3’s structure, photocycle, and molecular mechanism of proton transport.  My work applies a series of spectroscopic techniques including time resolved FTIR difference spectroscopy and near-IR resonance Raman spectroscopy with site-directed mutagenesis to compare the role of specific amino acid residues and water molecules in the structure and function of BR and AR3.  Recently, using FTIR difference spectroscopy, I have found important differences between BR and AR3 in the region beyond 3600 cm^-1 which reflects structural changes in internal water molecules which are thought to be essential to the BR proton pumping mechanism.  In addition, I have also found evidence that the proton uptake and Schiff base reprotonation mechanism which involves specific Asp and Glu residues may differ significantly from BR.  These results and continued works will help identify conserved elements in BR-like proton pumps as well as help to bioengineer improved variants of AR3 to optimize neural silencing and voltage sensing.