Association of Carbonic Anhydrase Activity with Carboxysomes Isolated from the Cyanobacterium Synechococcus PCC7942

Association of Carbonic Anhydrase Activity with Carboxysomes Isolated from the Cyanobacterium... The development of a simple method for the isolation of purified carboxysomes from the cyanobacterium Synechococcus PCC7942 has made it possible to identify a specific and inducible, intracellular carbonic anhydrase (CA) activity that is strongly associated with carboxysomes. This was shown, in part, through enzyme recovery experiments that indicated that a clear majority of a CA activity that is sensitive to the CA inhibitor ethoxyzolamide (I 50 = 4 μ m ) copurifies with a majority of the cell's ribulose-1,5-bisphosphate carboxylase/oxygenase activity in a highly purified pelletable fraction. Electron microscopy of this pelletable fraction revealed the presence of carboxysomes that were physically intact. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of carboxysome proteins showed that the large and small subunits of ribulose-1,5-bisphosphate carbosylase/oxygenase were clearly prominent and that several other minor proteins could be distinguished. The specific location of this carboxysomal CA activity is further reinforced by the finding that a previously isolated high CO 2 -requiring mutant, Type II/No. 68 (G.D. Price, M.R. Badger (1989) Plant Physiol 91: 514-525), displayed a 30-fold reduction in carboxysome-associated CA activity when tested under optimal conditions. Carboxysomal CA has the unusual property of being inactivated by dithiothreitol. The enzyme also requires 20 m m Mg 2+ (as MgSO 4 ) for near maximum activity; other divalent cations, such as Ca 2+ and Mn 2+ , also stimulate carboxysomal CA activity, but to a lesser extent than Mg 2+ . Results are discussed in relation to the role of carboxysomes in the CO 2 -concentrating mechanism in cyanobacteria and the role that carboxysomal CA activity appears to play in this process. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png

Association of Carbonic Anhydrase Activity with Carboxysomes Isolated from the Cyanobacterium Synechococcus PCC7942

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Publisher
American Society of Plant Biologist
Copyright
Copyright © 1992 by the American Society of Plant Biologists
ISSN
1532-2548
eISSN
0032-0889
D.O.I.
10.1104/pp.100.2.784
Publisher site
See Article on Publisher Site

Abstract

The development of a simple method for the isolation of purified carboxysomes from the cyanobacterium Synechococcus PCC7942 has made it possible to identify a specific and inducible, intracellular carbonic anhydrase (CA) activity that is strongly associated with carboxysomes. This was shown, in part, through enzyme recovery experiments that indicated that a clear majority of a CA activity that is sensitive to the CA inhibitor ethoxyzolamide (I 50 = 4 μ m ) copurifies with a majority of the cell's ribulose-1,5-bisphosphate carboxylase/oxygenase activity in a highly purified pelletable fraction. Electron microscopy of this pelletable fraction revealed the presence of carboxysomes that were physically intact. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of carboxysome proteins showed that the large and small subunits of ribulose-1,5-bisphosphate carbosylase/oxygenase were clearly prominent and that several other minor proteins could be distinguished. The specific location of this carboxysomal CA activity is further reinforced by the finding that a previously isolated high CO 2 -requiring mutant, Type II/No. 68 (G.D. Price, M.R. Badger (1989) Plant Physiol 91: 514-525), displayed a 30-fold reduction in carboxysome-associated CA activity when tested under optimal conditions. Carboxysomal CA has the unusual property of being inactivated by dithiothreitol. The enzyme also requires 20 m m Mg 2+ (as MgSO 4 ) for near maximum activity; other divalent cations, such as Ca 2+ and Mn 2+ , also stimulate carboxysomal CA activity, but to a lesser extent than Mg 2+ . Results are discussed in relation to the role of carboxysomes in the CO 2 -concentrating mechanism in cyanobacteria and the role that carboxysomal CA activity appears to play in this process.

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