Keynote Lecture
Deciphering the Extraordinary Energy Transfer Capabilities of the Phycobilisome Photosynthetic Light Harvesting Complex

The initial steps in biological photosynthetic solar energy conversion are performed by light harvesting complexes (LHC) that efficiently absorb light and perform energy transfer to the reaction centers. The phycobilisome (PBS) is the main LHC in cyanobacteria and red algae. PBS function is far more robust than typically assumed, performing energy transfer over large distances in a wide range of configurations and surroundings. We have determined high resolution structures of PBS components from a wide variety of cyanobacterial species and developed stabilization methods for analysis of higher level assemblies. This allows the analyses of isolated components and the entire PBS using: crystallography and cryo-TEM [1] solution [2] and surface spectroscopies [3] and coupled cross-linking/MS [4, 5]. The functional robustness of the PBS components suggests that they could be used in non-biological devices involving long range excitonic coupling. Using these methods, we are able to model the PBS and propose energy transfer pathways. In addition, we have recently analyzed the interaction between the Orange Carotenoid Protein (OCP) and the PBS and based on the identified constraints we have suggested a possible mechanism by which the OCP drastically decreases the flow of energy from the PBS to the reaction centers [5].

Acknowledgements: this work is supported by the US-Israel Bi-National Science Foundation (2014395) and the Israel Science Foundation (1576/12)

References

[1] L. David et al. Biochim. et Biophys. Acta 1837:385-389 (2014).

[2] C. Nganou, et al. Photochem. and Photobiol. Sci. 14:429-438 (2015).

[3] I. Eisenberg et. al. Phys. Chem. Chem. Phys., 16: 11196-11201 (2014).

[4] O. Tal et al. J. Biol. Chem, 289:33084-33097 (2014).

[5] D. Harris et al. Proc. Natl. Acad. Sci. USA, 113(12), E1655-1662 (2016).