Structural studies of chlorophyll f-based photosynthesis
File(s)
Author(s)
Consoli, Giovanni
Type
Thesis
Abstract
Photosynthesis is the central biochemical process that sustains life on Earth. It captures
solar energy to drive charge separation and water oxidation, releasing molecular oxygen
as a byproduct, energising the atmosphere, and enabling complex life. The reduced carbon
compounds it produces support global food webs as biomass and, over geological
timescales, have shaped human civilisation through the formation of fossil fuels. In recent
decades, photosynthetic organisms capable of harvesting longer-wavelength photons have
been identified, prompting academic interest in characterising their mechanisms and
assessing their potential for use in photosynthetic bioprocesses. However, given the
stringent energy requirements of canonical oxygenic photosynthesis, it is essential to
assess the advantages and limitations of the evolutionary strategies that enable the same
photochemical reactions to occur with less energetic photons. Understanding light
harvesting, charge separation, and the spatial arrangement of long-wavelength pigments
requires structural insights into the light-driven components of far-red-light-adapted
photosynthetic machinery.
In this work, the structures of Photosystem I and Photosystem II from the chlorophyll fcontaining
cyanobacterium Chroococcidiopsis thermalis PCC 7203 were determined using
single-particle cryo-electron microscopy. The locations of all eight chlorophyll f sites in
FR-PSI, including the A-1B reaction centre pigment, and all four chlorophyll f sites plus the
chlorophyll d primary donor in FR-PSII, are proposed based on chemical environments,
conserved sequence changes, and detailed analysis of electrostatic potential maps. This
study also reports the identification and structural characterisation of a novel FR-PSII
subunit encoded within the FaRLiP cluster.
The structure of the intact far-red-light-adapted allophycocyanin antenna has also been
solved, and the evolutionary adaptations that allow efficient management of excitation
energy transfer in the far-red-light-adapted photosynthetic apparatus discussed. Finally,
the phytochrome responsible for regulating far-red light photoacclimation has been
expressed and a mathematical model that describes its behaviour under varying light
conditions is presented.
solar energy to drive charge separation and water oxidation, releasing molecular oxygen
as a byproduct, energising the atmosphere, and enabling complex life. The reduced carbon
compounds it produces support global food webs as biomass and, over geological
timescales, have shaped human civilisation through the formation of fossil fuels. In recent
decades, photosynthetic organisms capable of harvesting longer-wavelength photons have
been identified, prompting academic interest in characterising their mechanisms and
assessing their potential for use in photosynthetic bioprocesses. However, given the
stringent energy requirements of canonical oxygenic photosynthesis, it is essential to
assess the advantages and limitations of the evolutionary strategies that enable the same
photochemical reactions to occur with less energetic photons. Understanding light
harvesting, charge separation, and the spatial arrangement of long-wavelength pigments
requires structural insights into the light-driven components of far-red-light-adapted
photosynthetic machinery.
In this work, the structures of Photosystem I and Photosystem II from the chlorophyll fcontaining
cyanobacterium Chroococcidiopsis thermalis PCC 7203 were determined using
single-particle cryo-electron microscopy. The locations of all eight chlorophyll f sites in
FR-PSI, including the A-1B reaction centre pigment, and all four chlorophyll f sites plus the
chlorophyll d primary donor in FR-PSII, are proposed based on chemical environments,
conserved sequence changes, and detailed analysis of electrostatic potential maps. This
study also reports the identification and structural characterisation of a novel FR-PSII
subunit encoded within the FaRLiP cluster.
The structure of the intact far-red-light-adapted allophycocyanin antenna has also been
solved, and the evolutionary adaptations that allow efficient management of excitation
energy transfer in the far-red-light-adapted photosynthetic apparatus discussed. Finally,
the phytochrome responsible for regulating far-red light photoacclimation has been
expressed and a mathematical model that describes its behaviour under varying light
conditions is presented.
Version
Open Access
Date Issued
2025-05-16
Date Awarded
2025-08-01
Copyright Statement
Attribution-Non Commercial-No Derivatives 4.0 International Licence (CC BY-NC-ND)
Advisor
Rutherford, A. William
Benoit, Chachuat
Sponsor
European Commission
Grant Number
955520
Publisher Department
Department of Life Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)