According to genomics up to 40% of all eukaryotic proteins are membrane bound. Their isolation from the biomembrane is essential for structural and functional studies. The major task in membrane protein isolation is obtaining a pure and homogeneous population, while maintaining biological activity, native conformation, and keeping cofactors bound. The major problem is the amphiphilic nature of membrane proteins, which require detergents for their solubilization.
This thesis is based on five papers describing the application of perfusion chromatography for membrane protein isolation. The method is optimized for speed, resolution and diversity. It is shown that membrane proteins can be isolated fast enough to keep biological activity and native conformation. The high resolution is demonstrated to give pure membrane protein populations with only one separation step, as well as the possibility to find new membrane protein subpopulations. The technical diversity of perfusion chromatography is shown by the fact that it can replace conventional chromatographic separation or fractionation techniques such as density centrifugation. The biological diversity in the applications of perfusion chromatography is shown by the different membrane proteins and model systems presented in this thesis.
The first model system presented is the thylakoid membrane and its photosynthetic membrane protein complexes. The second model system is the mammalian small intestine, whose biomembrane has a completelydifferent lipid composition. Perfusion chromatography is used for the purification of the highly abundant major photosynthetic complexes,large multisubunit integral membrane proteins, as well as differentsub-stoichiometricmembrane proteins, as pigment carriers, proteases and transporters. For the first time functional hypotheses could be experimentally confirmed.
All properties of perfusion chromatography are optimally used in chromatographic screening, the novel approach to rapid and rational design of membrane protein purification, as presented in this thesis.
Stockholm: Stockholm University , 1999. , 115 p.