Photosynthesis and photorespiration in a mutant of the cyanobacterium Synechocystis PCC 6803 lacking carboxysomes

A mutant of the cyanobacterium Synechocystis PCC 6803 was obtained by replacing the gene of the carboxylation enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) with that of the photosynthetic bacterium Rhodospirillum rubrum. This mutant consequently lacks carboxysomes - the protein co...

Full description

Saved in:
Bibliographic Details
Published in:Planta 1992-07, Vol.187 (4), p.511-516
Main Authors: Marcus, Y, Berry, J.A, Pierce, J
Format: Article
Language:English
Subjects:
Bacteriology
Badgers
Berries
Biological and medical sciences
Carbon
carbonates
Carboxylation
Cyanobacteria
Enzymes
Fundamental and applied biological sciences. Psychology
Glycolates
inorganic carbon compensation point
Life Sciences & Biomedicine
Metabolism. Enzymes
Microbiology
mutants
Photorespiration
Photosynthesis
Plant Sciences
Plants
Rhodospirillum rubrum
ribulose-bisphosphate carboxylase
Science & Technology
Synechocystis
translocation (plant physiology)
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:A mutant of the cyanobacterium Synechocystis PCC 6803 was obtained by replacing the gene of the carboxylation enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) with that of the photosynthetic bacterium Rhodospirillum rubrum. This mutant consequently lacks carboxysomes - the protein complexes in which the original enzyme is packed. It is incapable of growing at atmospheric CO2 levels and has an apparent photosynthetic affinity for inorganic carbon (C(i)) which is 1000 times lower than that of the wild type, yet it accumulates more C(i) than the wild type. The mutant appears to be defective in its ability to utilize the intracellular C(i) pool for photosynthesis. Unlike the carboxysomal carboxylase activity of Rubisco, which is almost insensitive to inhibition by O2 in vitro, the soluble enzyme is competitively inhibited by O2. The photosynthetic rate and C(i) compensation point of the wild type were hardly affected by low O2 levels. Above 100 micromolar O2, however, both parameters became inhibited. The CO2 compensation point of the mutant was linearly dependent on O2 concentration. The higher sensitivity of the mutant to O2 inhibition than that expected from in-vitro kinetics parameters of Rubisco, indicates a low capacity to recycle photorespiratory metabolites to Calvin-cycle intermediates.
ISSN:0032-0935
1432-2048
DOI:10.1007/bf00199970