Abstract
Efficient proton removal from the oxygen-evolving complex (OEC) of photosystem II (PSII) and activation of substrate water molecules are some of the key aspects optimized in the OEC for high turnover rates. The hydrogen-bonding network around the OEC is critical for efficient proton transfer and for tuning the position and pKa values of the substrate water/hydroxo/oxo molecules. The D1-N181 residue is part of the hydrogen-bonding network on the active face of the OEC. D1-N181 is also associated with the chloride ion in the D2-K317 site and is one of the residues closest to a putative substrate water molecule bound as a terminal ligand to Mn4. We studied the effect of the D1-N181A and D1-N181S mutations on the water oxidation chemistry at the OEC. PSII core complexes isolated from the D1-N181A and D1-N181S mutants have steady-state O2 evolution rates lower than those of wild-type PSII core complexes. Fourier transform infrared spectroscopy indicates slight perturbations of the hydrogen-bonding network in D1-N181A and D1-N181S PSII core complexes, similar to the effects of some other mutations in the same region, but to a lesser extent. Unlike in wild-type PSII core complexes, a g = 4 signal was observed in the S2-state EPR spectra of D1-N181A and D1-N181S PSII core complexes in addition to the normal g = 2 multiline signal. The S-state cycling of D1-N181A and D1-N181S PSII core complexes was similar to that of wild-type PSII core complexes, whereas the O2-release kinetics of D1-N181A and D1-N181S PSII core complexes were much slower than the O2-release kinetics of wild-type PSII core complexes. On the basis of these results, we conclude that proton transfer is not compromised in the D1-N181A and D1-N181S mutants but that the O-O bond formation step is retarded in these mutants.
| Original language | English |
|---|---|
| Pages (from-to) | 1663-1672 |
| Number of pages | 10 |
| Journal | Biochemistry |
| Volume | 54 |
| Issue number | 8 |
| DOIs | |
| Publication status | Published - Mar 3 2015 |
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ASJC Scopus subject areas
- Biochemistry
- Medicine(all)
Cite this
Probing the effect of mutations of asparagine 181 in the D1 subunit of photosystem II. / Pokhrel, Ravi; Debus, Richard J.; Brudvig, Gary W.
In: Biochemistry, Vol. 54, No. 8, 03.03.2015, p. 1663-1672.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Probing the effect of mutations of asparagine 181 in the D1 subunit of photosystem II
AU - Pokhrel, Ravi
AU - Debus, Richard J.
AU - Brudvig, Gary W
PY - 2015/3/3
Y1 - 2015/3/3
N2 - Efficient proton removal from the oxygen-evolving complex (OEC) of photosystem II (PSII) and activation of substrate water molecules are some of the key aspects optimized in the OEC for high turnover rates. The hydrogen-bonding network around the OEC is critical for efficient proton transfer and for tuning the position and pKa values of the substrate water/hydroxo/oxo molecules. The D1-N181 residue is part of the hydrogen-bonding network on the active face of the OEC. D1-N181 is also associated with the chloride ion in the D2-K317 site and is one of the residues closest to a putative substrate water molecule bound as a terminal ligand to Mn4. We studied the effect of the D1-N181A and D1-N181S mutations on the water oxidation chemistry at the OEC. PSII core complexes isolated from the D1-N181A and D1-N181S mutants have steady-state O2 evolution rates lower than those of wild-type PSII core complexes. Fourier transform infrared spectroscopy indicates slight perturbations of the hydrogen-bonding network in D1-N181A and D1-N181S PSII core complexes, similar to the effects of some other mutations in the same region, but to a lesser extent. Unlike in wild-type PSII core complexes, a g = 4 signal was observed in the S2-state EPR spectra of D1-N181A and D1-N181S PSII core complexes in addition to the normal g = 2 multiline signal. The S-state cycling of D1-N181A and D1-N181S PSII core complexes was similar to that of wild-type PSII core complexes, whereas the O2-release kinetics of D1-N181A and D1-N181S PSII core complexes were much slower than the O2-release kinetics of wild-type PSII core complexes. On the basis of these results, we conclude that proton transfer is not compromised in the D1-N181A and D1-N181S mutants but that the O-O bond formation step is retarded in these mutants.
AB - Efficient proton removal from the oxygen-evolving complex (OEC) of photosystem II (PSII) and activation of substrate water molecules are some of the key aspects optimized in the OEC for high turnover rates. The hydrogen-bonding network around the OEC is critical for efficient proton transfer and for tuning the position and pKa values of the substrate water/hydroxo/oxo molecules. The D1-N181 residue is part of the hydrogen-bonding network on the active face of the OEC. D1-N181 is also associated with the chloride ion in the D2-K317 site and is one of the residues closest to a putative substrate water molecule bound as a terminal ligand to Mn4. We studied the effect of the D1-N181A and D1-N181S mutations on the water oxidation chemistry at the OEC. PSII core complexes isolated from the D1-N181A and D1-N181S mutants have steady-state O2 evolution rates lower than those of wild-type PSII core complexes. Fourier transform infrared spectroscopy indicates slight perturbations of the hydrogen-bonding network in D1-N181A and D1-N181S PSII core complexes, similar to the effects of some other mutations in the same region, but to a lesser extent. Unlike in wild-type PSII core complexes, a g = 4 signal was observed in the S2-state EPR spectra of D1-N181A and D1-N181S PSII core complexes in addition to the normal g = 2 multiline signal. The S-state cycling of D1-N181A and D1-N181S PSII core complexes was similar to that of wild-type PSII core complexes, whereas the O2-release kinetics of D1-N181A and D1-N181S PSII core complexes were much slower than the O2-release kinetics of wild-type PSII core complexes. On the basis of these results, we conclude that proton transfer is not compromised in the D1-N181A and D1-N181S mutants but that the O-O bond formation step is retarded in these mutants.
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U2 - 10.1021/bi501468h
DO - 10.1021/bi501468h
M3 - Article
VL - 54
SP - 1663
EP - 1672
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 8
ER -