Structure-based Hamiltonian model for IsiA uncovers a highly robust pigment-protein complex

Hanan Schoffman, William M. Brown, Yossi Paltiel, Nir Keren*, Erik M. Gauger*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The iron stress-induced protein A (IsiA) is a source of interest and debate in biological research. The IsiA supercomplex, binding over 200 chlorophylls, assembles in multimeric rings around photosystem I (PSI). Recently, the IsiA-PSI structure from Synechocystis sp. PCC 6803 was resolved to 3.48 Å. Based on this structure, we created a model simulating a single excitation event in an IsiA monomer. This model enabled us to calculate the fluorescence and the localization of the excitation in the IsiA structure. To further examine this system, noise was introduced to the model in two forms - thermal and positional. Introducing noise highlights the functional differences in the system between cryogenic temperatures and biologically relevant temperatures. Our results show that the energetics of the IsiA pigment-protein complex are very robust at room temperature. Nevertheless, shifts in the position of specific chlorophylls lead to large changes in their optical and fluorescence properties. Based on these results, we discuss the implication of highly robust structures, with potential for serving different roles in a context-dependent manner, on our understanding of the function and evolution of photosynthetic processes.

Original languageAmerican English
Article number20200399
JournalJournal of the Royal Society Interface
Issue number169
StatePublished - 16 Aug 2020

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© 2020 The Author(s).


  • iron stress-induced protein A
  • photosynthetic complex
  • structure-based Hamiltonian model


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