Biological complexity: new complex photosynthesis molecule (Introduction)

by David Turell , Monday, May 27, 2019, 22:39 (2007 days ago) @ David Turell

Very large, very complex group of photosynthetic proteins described:

https://phys.org/news/2019-05-scientists-photosynthetic-supercomplex.html

The paper is titled "The structure of the stress induced photosystem I—IsiA antenna supercomplex."

"'Supercomplexes are associations between antennae proteins and photochemical reaction centers that exist in all photosynthetic organisms," explained Yuval Mazor, an assistant professor in the School of Molecular Sciences and the Biodesign Institute's Center for Applied Structural Discovery. "This particular one comes from cyanobacteria, the class (phyla) of bacteria in which oxygenic photosynthesis first appeared (a few billion years ago) and later evolved, into all types of oxygenic photosynthesis that we know today."

***

"In the lab, this particular super-complex is produced by cyanobacteria under low iron environment or excessive light fluxes. However, in the "real world" iron exists at very low concentrations and high light can be the rule rather than the exception, so ultimately PSI-IsiA is a very 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.

"There are 591 chlorophylls in the PSI-IsiA supercomplex, by far the largest number of bound pigments in any of the photosynthetic super-complexes with known structures.

"The ability of cyanobacteria to express this complex when they are under stress plays an important role in their survival under these conditions. This complex also represents a large class of antennae that are very common in marine cyanobacteria, which are responsible for a considerable fraction of the total global photosynthesis output (estimates vary between 15% and 25%). Mazor emphasizes that their work was done on a common laboratory strain, not on one of the marine species.

"The current structure uncovers the most crucial details of this enormous machine. As the first example from the cyanobacterial branch of the membrane embedded antenna proteins, it lays a path for evaluating the light-harvesting and photoprotection mechanism (from excess or fluctuating light conditions) in cyanobacteria."

Comment: Unfortunately no diagram, but the enormous complexity is obvious from the description. There is no way this arrangement could be developed by chance. It must be designed