Isolation and Immunological Characterization of a Carotenoid-Binding Protein from the Cyanobacteria Synechocystis Sp. PCC6714 and Anacystis Nidulans R2

Abstract

Cyanobacteria are photoautotrophic prokaryotes which contain external and internal membrane systems which are structurally and functionally distinct. The cyanobacterial cell is delimited by a Gram-negative double-membrane envelope (1,2); within the cytoplasm are concentric layers of chlorophyll-binding thylakoid membranes which serve as the site for photosynthetic electron transport and ATP synthesis (3). Recent work on Anacystis nidulans and Synechocystis sp. PCC6714 described methods for the separation of the cytoplasmic membrane from both the cell wall and the thylakoids (2,4). Purified cyanobacterial cytoplasmic membranes are yellow-orange due to the presence of carotenes and xanthophylls (2,4,5). in this study, we have identified a carotenoid-binding protein which is a major component of the Synechocystis sp. PCC6714 cytoplasmic membrane. This strain is capable of photoheterotrophic growth; under these conditions, the cells grow in the presence of glucose and atrazine, a Photosystem II inhibitor. Photoheterotrophic cells, which are incapable of producing oxygen, utilize glucose as a carbon source and light as an energy source driving cyclic photophosphorylation around PSI (4). in this report we show that the carotenoid-protein accumulates only in autotrophically grown, oxygen-evolving Synechocystis sp. cultures.