Investigation of the PucC Protein from Rhodopseudomonas acidophila

Abstract

The non-sulphur photosynthetic bacteria Rps. acidophila when grown in the light synthesises lamellae like membranes within the cell. These ICM house the photosynthetic RC and the antenna complexes, LH1 & LH2. LH1 and LH2 gather light energy and feed this energy into the RC where it is used to instigate charge separation. Subsequently, this is used to create a proton gradient across the membrane which drives the synthesis of ATP in the cell. Recently, several advances in the field of protein crystallography have been made with regard to the structure of bacterial light harvesting apparatus. The three dimensional structures of the LH2 from Rps. acidophila strain 10050 (1) and Rhodospirillum molischianum (2) and the lower resolution two dimensional structure of the LH1 from Rhodospirillum rubrum (3) have added to the three dimensional structures of the RC from Rhodobacter sphaeroides (4) and Rhodopseudomonas viridis (5). These structures have provided a basis on which the purple bacteria’s photosynthetic apparatus has been modelled (6). The question which arises from these structural studies is “How are the complexes assembled in the membrane?” When the photosynthetic membranes are solubilised with a suitable detergent only fully assembled RCs and antenna complexes are found. Firstly considering the antenna complexes, studies with Rhodobacter capsulatus have suggested that the pucC gene associated with the pucBA genes (which encode the LH2 α and β polypeptides) is involved in the assembly of the LH2 complex (7).