Separation and characterization of thylakoid and cell envelope of the blue green alga cyanobacterium anacystis nidulans
Murata, N.; Sato, N.; Omata, T.; Kuwabara, T.
Plant and Cell Physiology 22(5): 855-866
The thylakoid and the cell envelope of the blue-green alga A. nidulans were separated by mechanical disruption of lysozyme-treated cells followed by differential and density gradient centrifugation. The prepared envelope was composed of an outer membrane, a peptidoglycan layer and possibly a part of the cytoplasmic membrane. The prepared thylakoid retained the size and intricate structure typical of the thylakoid membrane of this alga. Light absorption and fluorescence spectra revealed that the envelope contained carotenoids, a pigment with an absorption maximum at 748 nm (P750) and a small amount of pheophytin-like pigment with an absorption maximum at 673 nm. The thylakoid contained chlorophyll a and carotenoids but no P750. The thylakoid contained 5 kinds of carotenoids, the major ones being .beta.-carotene and zeaxanthin, whereas the cell envelope contained 2 kinds of carotenoids, zeaxanthin and nostoxanthin. Four kinds of lipids, abundant in the blue-green algae, were present in both the thylakoid and the cell envelope. The content of sulfolipid was very low in the cell envelope. The polypeptide compositions differed between the thylakoid and the cell envelope. Similarities between blue-green algal cells and eukaryotic chloroplasts are discussed with respect to the spectrophotometric and biochemical characteristics of the thylakoid and the envelope.