Immunocytochemical localization of glutamine synthetase in Rhodobacter capsulatus E1F1 and Rhodopseudomonas acidophila

Intracellular localization of glutamine synthetase has been studied by immunochemical techniques with cryosections and London Resin sections of Rhodobacter capsulatus E1F1 and Rhodopseudomonas acidophila. For immunostaining, sections were sequentially incubated with monospecific anti-glutamine synthetase antibodies (R. capsulatus) and gold labelled goat anti-rabbit antibodies. Gold label was present in the cytoplasm but not in the cell walls. The antigen is not associated with the cell membrane or with photosynthetic vesicle whether these are round and randomly distributed (R. capsulatus) or flattened and organized in well defined stacks (R. acidophila). Our results also indicate that glutamine synthetase is absent from the central, nucleoid part of the cell. The enzyme is present in dense cytoplasmic patches, which appear to be RNA-ribosome-containing areas.Abbreviations GS glutamine synthetase - LR London Resin White