Probing the excitonic landscape of the Chlorobaculum tepidum Fenna-Matthews-Olson (FMO) complex: a mutagenesis approach.
In this paper we report the steady-state optical properties of a series of site-directed mutants in the Fenna-Matthews-Olson (FMO) complex of Chlorobaculum tepidum, a photosynthetic green sulfur bacterium. The FMO antenna complex has historically been used as a model system for energy transfer due to the water-soluble nature of the protein, its stability at room temperature, as well as the availability of high-resolution structural data. Eight FMO mutants were constructed with changes in the environment of each of the bacteriochlorophyll a pigments found within each monomer of the homotrimeric FMO complex. Our results reveal multiple changes in low temperature absorption, as well as room temperature CD in each mutant compared to the wild-type FMO complex. These datasets were subsequently used to model the site energies of each pigment in the FMO complex by employing three different Hamiltonians from the literature. This enabled a basic approximation of the site energy shifts imparted on each pigment by the changed amino acid residue. These simulations suggest that, while the three Hamiltonians used in this work provide good fits to the wild-type FMO absorption spectrum, further efforts are required to obtain good fits to the mutant minus wild-type absorption difference spectra. This demonstrates that the use of FMO mutants can be a valuable tool to refine and iterate the current models of energy transfer in this system.
Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, United States; Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, MO 63130, United States.
Rafael G
RG
Saer
Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, United States.
Valentyn
V
Stadnytskyi
Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, United States; Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, MO 63130, United States; Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, United States.
Nikki C
NC
Magdaong
Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, United States.
Carrie
C
Goodson
Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, United States.
Sergei
S
Savikhin
Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, United States; Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, MO 63130, United States; Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, United States. Electronic address: blankenship@wustl.edu.
Robert E
RE
Blankenship
D001426:Bacterial Proteins / Q000737:chemistry*; D002942:Circular Dichroism; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D016297:Mutagenesis, Site-Directed
D001426:Bacterial Proteins; C086320:FMO bacteriochlorophyll protein, Bacteria; D045342:Light-Harvesting Protein Complexes
Bacteriohlorophyll; Exciton; Fenna-Matthews-Olson; Photosynthesis; Site-directed mutagenesis; Spectroscopy