For their own study, Dr. Matsumura and his colleagues decided to use a process called di-rected evolution which involved isolating and randomly mutating genes, and then inserting the mutated genes into bacteria (in this case Escherichia coli, or E. coli). They then screened the resulting mutant proteins for the fastest and most efficient enzymes. We decided to do what nature does, but at a much faster pace. Dr. Matsumura says. Essentially were using evolu-tion as a tool to engineer the protein.

Because E. coli does not normally participate in photosynthesis or carbon dioxide conversion, it does not usually carry the RuBisCO enzyme. In this study, Matsumuras team added the genes encoding RuBisCO and a helper enzyme to E. coli, enabling it to change carbon dioxide into con-sumable energy. The scientists withheld other nutrients from this genetically modified organism so that it would need RuBisCO and carbon dioxide to survive under these stringent conditions.

They then randomly mutated the RuBisCO gene, and added these mutant genes to the modified E. coli. The fastest growing strains carried mutated RuBisCO genes that produced a larger quantity of the enzyme, leading to faster assimilation of carbon dioxide gas. These mutations caused a 500 percent increase in RuBisCO expression Dr. Matsumura says. We are excited because such large changes could potentially lead to faster plant growth. This results also suggests that the en-zyme is evolving in our laboratory in the same way that it did in nature.

Even as these results are published, Matsumura and his team are continuing their research on the RuBisCO enzyme. To start, theyll experiment with increasing mutatio
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Contact: Holly Korschun
hkorsch@emory.edu
404-727-3990
Emory University Health Sciences Center
15-Feb-2006