The efficiency of the light harvesting antenna system in purple photosynthetic bacteria, at greater than 90%, is remarkable. A prerequisite to full understanding of this efficiency is a detailed structural knowledge of the major components of the antenna system, LH1, LH2, and the Reaction Center (RC), which are all membrane proteins. The structure of LH1 is only known to a resolution of 4.8A, and is less-well characterized than LH2 and the RC alone. This proposal outlines plans to obtain moderate to high-resolution structural detail of the LH1 system and the related LH1-RC complex, by utilizing Solid State Nuclear Magnetic Resonance (SS NMR) under conditions of Magic Angle Spinning (MAS) in conjunction with two- and three-dimensional NMR experiments and selective isotopic labeling of protein samples. The methodology employs SS NMR to obtain sequence-specific assignments of the amino acid residues of all constituents of the LH1 system, using these assignments and additional NMR experiments to determine structural constraints. The proposed study will provide information about photosynthesis and a further test of SS NMR methods to the study of membrane proteins - a crucial area of biochemical research with significant applications in the medical field.
