Isolation and Characterization of A Carotenoid-Associated Membrane Protein from The Cyanobacterium, Anacystis Nidulans R2

Abstract

Cyanobacteria have three distinct membrane systems; the outer and inner (cytoplasmic) membranes comprise the cell envelopes, as in other gram-negative bacteria, whereas the internal thylakoid membrane system contains the components responsible for an oxygen-evolving electron transfer system unique among prokaryote (1). Using improved isolation techniques, envelope (outer and cytoplasmic) membranes have been separated from thylakoids in both A. nidulans (2, 3) and Synechosistis PCC6714 (4, 5) and have been shown to contain carotenoids but little or no chlorophyll. The major carotenoids of the isolated outer and cytoplasmic membranes were xanthophylls, whereas the major thylakoid-associated carotenoid was β-carotene (2–4). During nitrate-starvation in A. nidulans, the xanthophyll content of cells increases, whereas both β-carotene and thylakoid membrane content decreases (6).