How to study the structure and function of a membrane protein: The photon-driven proton pump, bacteriorhodopsin (BR)

Monday, October 24, 2011 — Poster Session I
Noon – 2:00 p.m.	Natcher Conference Center	NIBIB	BIOPHY-12

Authors

• P Smith
• J Kakareka
• C Meuse
• M Braiman
• R Hendler

Abstract

We have developed both new linear algebra-based procedures and computer controlled spectrographic instrumentation for obtaining absolute infrared (IR) and visible spectra for each intermediate in the BR photocycle. From these spectra, we were able to define the precise pathway of the proton as it electrogenically traverses the membrane, and to pinpoint where the ΔpH and membrane potential (ΔΨ) components of the protonmotive (PMF) force are formed. The PMF is used to drive ATP synthesis in all aerobic life forms from bacteria to mammals. We find that different proton paths are responsible for forming either a ΔpH or a ΔΨ. The relative amounts of the two can be regulated as needed for different environmental conditions. The BR pump is a prototype for respiratory chain driven pumps. In principle, the procedures described here could be adapted to these other systems.

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