Deciphering the remarkable functionalities of the phycobilisome

N. Adira, D. Harrisa, O. Tala, S. Bar Zvia, A. Lahava, L. Davida, R. Ben Harosha, D. Jalletb, A. Wilsona, D. Kirilovskya, R.E. Blankenshipc, I. Eisenbergd, N. Kerend, Y. Paltield, C. Nganoue
aSchulich Faculty of Chemistry, Technion, Technion City, Haifa 32000 Israel; bInstitute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Univ Paris-Saclay, 91198 Gif sur Yvette, France; cDepartments of Biology and Chemistry, Washington University in St. Louis, St. Louis, MO, USA; dApplied Physics Department, The Hebrew University of Jerusalem, Israel; eVerschuren Centre for Sustainability in Energy and the Environment, Cape Breton University, Nova Scotia, Canada

The phycobilisome (PBS) pigment-protein complex is the main antenna in cyanobacteria and red algae. PBS function is far more robust than typically assumed, performing internal energy transfer over large distances in a wide spectrum of configurations and surroundings. In addition to the determination of high resolution structures of isolated PBS components from a wide variety of cyanobacterial species, we have developed cross-linking methods for stabilization of the PBS in low salt without losing functionality, allowing the analyses of the entire PBS using: crystallography, single particle reconstruction from Cryo-TEM images [1], ultra-fast [2] and high-resolution surface spectroscopies [3]. We have utilized these structures to suggest the unique properties of the PBS, and to identify the differences between species that live in different environments. The robustness of the PBS components suggests that they could be used in non-biological settings according to quantum principles.

Analysis of high-resolution dynamics in the PBS under different conditions is an additional complication that requires additional methods. We have applied coupled cross-linking/mass spectrometry to address such issues. We have used this method to identify more precisely the interaction interfaces between subunits along the energy transfer pathway [4]. In addition, we have recently analyzed the interaction between the Orange Carotenoid Protein 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.

Acknowledgements

This work is supported by the US-Israel Bi-National Science Foundation (2009406 and 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)