Functional hybrid Rubisco enzymes with plant small subunits and algal large subunits: engineered RbcS cDNA for expression in Chlamydomonas
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Publication Date
2010-04-27ISSN
0021-9258
Publisher
The Journal of Biological Chemistry
Language
en_US
Type
Article
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Genkov, T., Meyer, M., Griffiths, H., & Spreitzer, R. J. (2010). Functional hybrid Rubisco enzymes with plant small subunits and algal large subunits: engineered RbcS cDNA for expression in Chlamydomonas.
Abstract
There has been much interest in the chloroplast-encoded large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) as a target for engineering an increase in net CO2
fixation in photosynthesis. Improvements in the enzyme would lead to an increase in the production of food, fiber, and renewable energy. Although the large subunit contains the active site, a family of RbcS nuclear genes encodes the Rubisco small subunits, which can also influence the carboxylation catalytic efficiency and CO2/O2 specificity of the enzyme. To further define the role of the small subunit in Rubisco function, small subunits from spinach, Arabidopsis, and sunflower were assembled with algal large subunits by transformation of a Chlamydomonas reinhardtii mutant that lacks the RbcS gene family. Foreign RbcS cDNAs were successfully expressed in Chlamydomonas by fusing them to a Chlamydomonas RbcS transit peptide sequence engineered to contain rbcS introns. Although plant Rubisco
generally has greater CO2/O2 specificity but a lower carboxylation Vmax than Chlamydomonas Rubisco, the hybrid enzymes
have 3–11% increases in CO2/O2 specificity and retain near normal Vmax values. Thus, small subunits may make a significant
contribution to the overall catalytic performance of Rubisco.Despite having normal amounts of catalytically proficient
Rubisco, the hybrid mutant strains display reduced levels of photosynthetic growth and lack chloroplast pyrenoids. It appears that small subunits contain the structural elements responsible for targeting Rubisco to the algal pyrenoid, which is the site where CO2 is concentrated for optimal photosynthesis.
Sponsorship
This work was supported in part by Grant DE-FG02-00ER15044 from the United States Department of Energy.
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This record's URL: http://www.dspace.cam.ac.uk/handle/1810/226623
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