9809918 Loach The major membrane complexes that accomplish the capture of light energy in bacterial photosynthesis are the reaction center (RC) and the core light-harvesting complex (LH1). Even though the 3-dimensional structures of the RC and LH2 (closely related to LH1) are known, the contributions of the various stabilizing interactions have not been measured. The investigator's laboratory has reversibly dissociated LH1 and reconstituted it from its fundamental components, thus enabling the determination of stabilizing interactions by utilizing analogs of bacteriochlorophyll (Bchl) and the protein. Part of the projected research will complete the measurement of these stabilizing interactions. Several key questions as to how the RC, LH1, and bc1 complexes function together are now being addressed. One of this investigator's current major goals is to learn how reducing equivalents of the RC (ubihydroquinol) are made available to the bc1 complex. In some photosynthetic bacteria (e.g., Rhodobacter sphaeroides) a protein coded for by the pufX gene is involved in assisting this process. The investigator has isolated this protein from two different bacteria and characterized its effect on LH1 formation. In continuing work, the major domains of the Puf X protein are being chemically synthesized in order to evaluate regions showing specific interaction with LH1. Quantitative knowledge of stabilizing interactions is essential for full understanding of how the RC and LH1 function. Completion of the investigator's measurements of these stabilizing forces in LH1 will provide the first full description of such a membrane complex. This kind of knowledge is fundamental to understanding membrane complexes in general, and for engineering new complexes to carry out specific tasks. Determination of the role of the PufX protein in controlling the movement of reducing equivalents from the RC to the bc1 complex will provide an important insight into the regulation of light energy capture and seco ndary electron transport.
