Phylogenetic and spectroscopic insights on the evolution of core antenna proteins in cyanobacteria

Inhomogeneous energy transfer dynamics from iron-stress-induced protein A to photosystem I

“…IsiA can be isolated in aggregated or monomeric solubilized state and its spectroscopic properties can vary depending on the sample preparation and conditions ( Biswas et al., 2023 ). The monomeric IsiA complexes had absorption spectra with a maximum at 670 nm, whereas IsiA aggregates displayed an absorption maximum at 672 nm and a shoulder around 682 nm ( Supplementary Figure S1 ).…”

“…While it is well established that IsiA absorbs light at shorter wavelengths than PSI, there is substantial spectral overlap between them that, combined with the excitation dynamics within the respective antenna systems, makes quantitative treatment of the dynamics of energy transfer non-trivial. Another complication is the spectral variability of isolated IsiA, as reviewed by Biswas et al. (2023) .…”

“…While it is well established that IsiA absorbs light at shorter wavelengths than PSI, there is substantial spectral overlap between them that, combined with the excitation dynamics within the respective antenna systems, makes quantitative treatment of the dynamics of energy transfer non-trivial. Another complication is the spectral variability of isolated IsiA, as reviewed by Biswas et al (2023). For instance, the existence of red-shifted Chl states in IsiA aggregates but not in monomers, which is apparent from their absorption spectra, has been shown by fluorescence spectroscopy of IsiA aggregates at 5 K (Van Der Weij-De et al, 2007) and, more recently, by 5 K absorption and hole-burning spectroscopy of IsiA monomers, aggregates and PSI-IsiA (Reinot et al, 2022).…”

“…Recent high-resolution structures of isolated PSI–IsiA supercomplexes ( Toporik et al., 2019 ; Akita et al., 2020 ; Cao et al., 2020 ; Nagao et al., 2023 ), bring insight into the potential pathways of excitation energy transfer (EET) from IsiA to PSI. The IsiA monomer resembles CP43 of PSII, presumably evolved from a common ancestor protein ( Biswas et al., 2023 ), lacks the loop connecting helices V and VI. It coordinates 17 Chls, 13 of which in positions similar to CP43.…”