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- Title
Mutation of a metal ligand stabilizes the high-spin form of the S<sub>2</sub> state in the O<sub>2</sub>-producing Mn<sub>4</sub>CaO<sub>5</sub> cluster of photosystem II.
- Authors
Chakarawet, Khetpakorn; Debus, Richard J.; Britt, R. David
- Abstract
The residue D1-D170 bridges Mn4 with the Ca ion in the O2-evolving Mn4CaO5 cluster of Photosystem II. Recently, the D1-D170E mutation was shown to substantially alter the Sn+1-minus-Sn FTIR difference spectra [Debus RJ (2021) Biochemistry 60:3841-3855]. The mutation was proposed to alter the equilibrium between different Jahn–Teller conformers of the S1 state such that (i) a different S1 state conformer is stabilized in D1-D170E than in wild-type and (ii) the S1 to S2 transition in D1-D170E produces a high-spin form of the S2 state rather than the low-spin form that is produced in wild-type. In this study, we employed EPR spectroscopy to test if a high-spin form of the S2 state is formed preferentially in D1-D170E PSII. Our data show that illumination of dark-adapted D1-D170E PSII core complexes does indeed produce a high-spin form of the S2 state rather than the low-spin multiline form that is produced in wild-type. This observation provides further experimental support for a change in the equilibrium between S state conformers in both the S1 and S2 states in a site-directed mutant that retains substantial O2 evolving activity.
- Subjects
PHOTOSYSTEMS; ELECTRON paramagnetic resonance spectroscopy; LIGANDS (Biochemistry); METALS; FOURIER transform infrared spectroscopy
- Publication
Photosynthesis Research, 2023, Vol 156, Issue 3, p309
- ISSN
0166-8595
- Publication type
Article
- DOI
10.1007/s11120-023-00998-z