Purification and Fractionation of Membranes for Proteomic Analyses

Proteomics is a very powerful approach to link the information containe3|d in sequenced genomes, such as Arabidopsis , to the functional knowledge provided by studies of plant cell compartments. However, membrane proteomics remains a challenge. One way to bring into view the complex mixture of proteins present in a membrane is to develop proteomic analyses based on (1) the use of highly purified membrane fractions and (2) fractionation of membrane proteins to retrieve as many proteins as possible (from the most to the less hydrophobic ones). To illustrate such strategies, we choose two types of membranes, the plasma membrane and the chloroplast envelope membranes. Both types of membranes can be prepared in a reasonable degree of purity from different types of tissues: the plasma membrane from cultured cells and the chloroplast envelope membrane from whole plants. This article is restricted to the description of methods for the preparation of highly purified and characterized plant membrane fractions and the subsequent fractionation of these membrane proteins according to simple physicochemical criteria (i.e., chloroform/methanol extraction, alkaline or saline treatments) for further analyses using modern proteomic methodologies.