Robert Blankenship, PhD, PARC's director and the Lucille P. Markey Distinguished Professor of Arts & Sciences, said that one outcome of the work in the long term might be the ability to double or triple the efficiency of crop plants now stuck at a woeful 1 to 3 percent. "We will need such a boost to feed the 9 or 10 billion people predicted to be alive by 2050," he said.
Wizards of the lab
The scientists worked with the model organism often used to study photosynthesis in the lab, a cyanobacterium, sometimes called a blue-green alga.
Cyanobacteria are ancient organisms, known from fossils that are 3.5 billion years old, nearly as old as the oldest known rocks, and thought to be the first organisms to release oxygen into the noxious primitive atmosphere.
All photosynthesizing organisms have light-harvesting anntenas made up of many molecules that absorb light and transfer the excitation energy to reaction centers, where it is stored as charge separation.
In free-living cyanobacteria the antenna, called a phycobilisome, consists of splayed rods made up of disks of proteins containing intensely colored bilin pigments. The antenna sits directly above one reaction center, Photosystem II, and kitty corner to the other, Photosystem I.
PARC research scientist Haijun Liu, PhD, proposed stitching together the megacomplex and then engineered a strain of cyanobacteria that has a tag on the bottom of Photosystem II.
The mutant cells were treated with reagents that stitched together the complexes, then broken open, and the tag used to pull out Photosystem II and anything attached to it.
To figure out how the proteins were interconnected, the scientists repeatedly cut or shattered the proteins, analyzing them by mass spectrometry down to the level of the individual amino acid.
The amino acid sequences derived in this way were then compared to known sequences within the megacomplex, and the lo
|Contact: Diana Lutz|
Washington University in St. Louis