In vivo photoinactivation of ribulose bisphosphate carboxylase in the gas-vacuolate cyanobacteriumMicrocystis aeruginosa

Planta ◽  
1980 ◽  
Vol 149 (4) ◽  
pp. 411-412 ◽  
Author(s):  
Robert Stewart ◽  
Geoffrey A. Codd
Keyword(s):  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase

Immunolocalization of Rubisco Activase and Rubisco in C3 and C4 Plant Tissues

2000 ◽  
Vol 6 (S2) ◽  
pp. 472-473
Author(s):  
S. Madhavan ◽  
M. S. Miller-Goodman ◽  
K. W. Lee
Keyword(s):  
Higher Plants ◽  
Tight Binding ◽  
Rubisco Activase ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate Carboxylase Oxygenase ◽  
Microscopic Studies ◽  
Sugar Phosphates

Ribulose bisphosphate carboxylase/oxygenase (Rubisco), an abundant enzyme in chloroplasts, must be activated by CO2 in order for it to catalyze the carboxylation of ribulose bisphosphate. Rubisco activase, a nuclear encoded chloroplast protein was first identified as a biochemical lesion in the rca mutant of Arabidopsis (1) which lacked this enzyme. Study of Rubisco in this mutant (2) and transgenic tobacco plants with reduced Rubisco activase levels showed that Rubisco could not achieve and maintain an adequate level of activity, in vivo, without an activase. Rubisco activase promotes ‘activation’ of Rubisco by overcoming the deleterious effects of tight binding sugar phosphates and low chloroplast CO2 levels on catalysis and carbamylation (1).Rubisco activase has been detected in higher plants (3), in unicellular green algae (4,5) and in cyanobacteria (6). Though the presence of Rubisco in guard cell chlroplasts was a subject of controversy, several immunolight and immunoelectron microscopic studies have demonstrated the presence of Rubisco in guard cells (7).

scholarly journals Studies on the assembly of large subunits of ribulose bisphosphate carboxylase in isolated pea chloroplasts.

1982 ◽  
Vol 94 (1) ◽  
pp. 20-27 ◽  
Author(s):  
H Roy ◽  
M Bloom ◽  
P Milos ◽  
M Monroe
Keyword(s):  
Large Subunit ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Dissociation Reaction ◽  
Bisphosphate Carboxylase ◽  
In Organello ◽  
Intact Chloroplasts ◽  
Isolated Chloroplasts

Ribulose bisphosphate carboxylase consists of cytoplasmically synthesized "small" subunits and chloroplast-synthesized "large" subunits. Large subunits of ribulose bisphosphate carboxylase synthesized in vivo or in organello can be recovered from intact chloroplasts in the form of two different complexes with sedimentation coefficients of 7S and 29S. About one-third to one-half of the large subunits synthesized in isolated chloroplasts are found in the 7S complex, the remainder being found in the 29S complex. Upon prolonged illumination of the chloroplasts, newly synthesized large subunits accumulate in the 18S ribulose bisphosphate carboxylase molecule and disappear from both the 7S and the 29S large subunit complexes. The 29S complex undergoes an in vitro dissociation reaction and is not as stable as ribulose bisphosphate carboxylase. The data indicate that (a) the 7S large subunit complex is a chloroplast product, the (b) the 29S large subunit complex is labeled in vivo, that (c) each of these two complexes can account quantitatively for all the large subunits assembled into RuBPCase in organello, and that (d) excess large subunits are degraded in chloroplasts.

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