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Energetic Diversity in the Electron-Transfer Pathways of Type I Photosynthetic Reaction Centers.
- Source :
-
Biochemistry [Biochemistry] 2023 Feb 21; Vol. 62 (4), pp. 934-941. Date of Electronic Publication: 2023 Feb 07. - Publication Year :
- 2023
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Abstract
- Photosynthetic reaction centers from heliobacteria (HbRC) and green sulfur bacteria (GsbRC) are homodimeric proteins and share a common ancestor with photosystem I (PSI), classified as type I reaction centers. Using the HbRC crystal structure, we calculated the redox potential ( E <subscript>m</subscript> ) values in the electron-transfer branches, solving the linear Poisson-Boltzmann equation and considering the protonation states of all titratable sites in the entire protein-pigment complex. E <subscript>m</subscript> (A <subscript>-1</subscript> ) for bacteriochlorophyll g at the secondary site in HbRC (-1157 mV) is as low as E <subscript>m</subscript> (A <subscript>-1</subscript> ) for chlorophyll a in PSI (-1173 mV). E <subscript>m</subscript> (A <subscript>0</subscript> /HbRC) is at the same level as E <subscript>m</subscript> (A <subscript>0</subscript> /GsbRC) and is 200 mV higher than E <subscript>m</subscript> (A <subscript>0</subscript> /PSI) due to the replacement of PsaA-Trp697/PsaB-Trp677 in PSI with PshA-Arg554 in HbRC. In contrast, E <subscript>m</subscript> (F <subscript>X</subscript> ) for the Fe <subscript>4</subscript> S <subscript>4</subscript> cluster in HbRC (-420 mV) is significantly higher than E <subscript>m</subscript> (F <subscript>X</subscript> ) in GsbRC (-719 mV) and PSI (-705 mV) due to the absence of acidic residues that correspond to PscA-Asp634 in GsbRC and PsaB-Asp575 in PSI. It seems likely that type I reaction centers have evolved, adopting (bacterio)chlorophylls suitable for their light environments while maintaining electron-transfer cascades.
Details
- Language :
- English
- ISSN :
- 1520-4995
- Volume :
- 62
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 36749324
- Full Text :
- https://doi.org/10.1021/acs.biochem.2c00689