Scientists from Arizona State University have determined the structure of a
very large photosynthetic supercomplex, PSI-IsiA complex, a common form of
photosystem I, one of the two essential engines of photosynthesis.
The complex is unique in size, the largest photosynthetic supercomplex with
a known molecular structure, and in complexity with more than 700 different
molecules (mostly light-harvesting molecules) making up the complete
structure. The scientists also found that there are 591 chlorophylls in the
PSI-IsiA supercomplex, by far the largest number of bound pigments in any of
the photosynthetic supercomplexes with known structures.
This supercomplex is produced by a cyanobacterium under low iron environment
or excessive light fluxes in the lab. The ability of the cyanobacterium to
express this complex while under stress plays an important role in their
survival under such conditions.