FTIR spectroscopy of synechocystis 6803 mutants affected on the hydrogen bonds to the carbonyl groups of the PsaA chlorophyll of P700 supports an extensive delocalization of the charge in P700+

Biochemistry
Maria PantelidouJ Breton

Abstract

P700, the primary electron donor of photosystem I is an asymmetric dimer made of one molecule of chlorophyll a' (P(A)) and one of chlorophyll a (P(B)). While the carbonyl groups of P(A) are involved in hydrogen-bonding interactions with several surrounding amino acid side chains and a water molecule, P(B) does not engage in hydrogen bonding with the protein. Light-induced FTIR difference spectroscopy of the photooxidation of P700 has been combined with site-directed mutagenesis in Synechocystis sp. PCC 6803 to investigate the influence of these hydrogen bonds on the structure of P700 and P700(+). When the residue Thr A739, which donates a hydrogen bond to the 9-keto C=O group of P(A), is changed to Phe, a differential signal at 1653(+)/1638(-) cm(-1) in the P700(+)/P700 FTIR difference spectrum upshifts by approximately 30-40 cm(-1), as expected for the rupture of the hydrogen bond or, at least, a strong decrease of its strength. The same upshift is also observed in the FTIR spectrum of a triple mutant in which the residues involved in the three main hydrogen bonds to the 9-keto and 10a-carbomethoxy groups of P(A) have been changed to the symmetry-related side chains present around P(B). In addition, the spectrum of the triple ...Continue Reading

References

Nov 1, 2001·Biochimica Et Biophysica Acta·Y Deligiannakis, A W Rutherford

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Citations

Jun 25, 2005·Photosynthesis Research·Ingo Grotjohann, Petra Fromme
Jun 11, 2009·Photosynthesis Research·Catherine Berthomieu, Rainer Hienerwadel
Jan 21, 2006·The Journal of Chemical Physics·Peter CanfieldJeffrey R Reimers
Jul 22, 2008·Biophysical Journal·Shana L Bender, Bridgette A Barry
Mar 11, 2021·The Journal of Physical Chemistry. B·Koji MitsuhashiHiroshi Ishikita
May 26, 2005·Journal of the American Chemical Society·Colette A SackstederBridgette A Barry

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