Structure and Function of the Prochlorothrix Hollandica Photosynthetic Antenna System

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The photosynthetic prokaryote, Prochlorothrix hollandica, is the only free-living bacterium known which contains the higher plant antenna pigment chlorophyll b. This feature has initiated many comparative studies examining whether the P. hollandica antenna is structurally and functionally similar to that of higher plants. Previous studies from other laboratories have shown that thylakoid membrane stacking occurs in P. hollandica, a function ascribed to the LHCII antenna of green plant chloroplasts. Since the P. hollandica Chl a/b antenna is structurally simpler than chloroplast LHCII, this research studies the antenna proteins of P. hollandica to probe the structural basis for membrane stacking. The experimental approach combines molecular biological, biochemical and biophysical techniques to address the following specific questions: 1) What are the evolutionary relationships among accessory Chl-proteins?; 2) How do photosynthetic organisms adapt to changing light conditions?; and 3) What are the structural requirements for thylakoid membrane stacking?%%% The light reactions of oxygen evolving photosynthesis involve two kinds of membrane-bound pigment-binding complexes,those which are involved in the primary photochemistry and those which serve an accessory antenna function by harvesting light energy to be transferred to the primary systems. A great deal of information has been recently obtained about the chlorophyll-proteins. In contrast, the structure of many antenna complexes is not known to this high level of resolution. The focus of this research is to examine a class of prokaryotic antenna chlorophyll-proteins to help understand their synthesis, assembly and relatedness to chloroplast antennae systems.***