PNNL

Abstract

The intracytoplasmic membrane (ICM) system develops, upon induction, as a structure dedicated to the major events of bacterial photosynthesis, including harvesting light energy, primary charge separation, and electron transport. In this study, multi-chromatographic methods coupled with fourier transform ion cyclotron resonance (FTICR) mass spectrometer, combined with subcellular fractionation, was applied to an investigation of the supramolecular composition of the native photosynthetic membrane of Rhodobacter sphaeroides 2.4.1. A complete proteomic profile of the intracytoplasmic membranes was obtained and the results showed that the intracytoplasmic membranes are mainly composed of four photosynthetic membrane protein complexes, including light harvesting complexes I and II, the reaction center and cytochrome bc1, as well as two new membrane protein components, an unknown protein (RSP1760) and a possible alkane hydroxylase. Proteins necessary for various cellular functions, such as ATP synthesis, respiratory components, ABC transporters, protein translocation, and other proteins with unknown functions were also identified in association with the intracytoplasmic membranes. This study opens a new perspective on the characterization and understanding of the photosynthetic supramolecular complexes of R. sphaeroides, and their internal interactions as well as interactions with other proteins inside or outside the intracytoplasmic membranes.