Formate binding near the redox-active tyrosineD in photosystem II: consequences on the properties of tyrD.
Formate and phosphate affect substantially the rate of tyrosine D (TyrD) oxidation and the stability of the radical TyrD* in Photosystem II [Hienerwadel R, Boussac A, Breton J and Berthomieu C (1996) Biochemistry 35: 15447-15460]. This observation prompted us to analyze the influence of formate and phosphate on the environment of TyrD using FTIR spectroscopy. The nu (CO) IR mode of TyrD* at 1503 cm-1 remains unchanged whatever the buffer used at pH 6 and whether formate is present or not in the sample. Similarly, the main IR mode of reduced TyrD remains at approximately 1250 cm-1 in all tested conditions. We thus conclude that formate does not modify the hydrogen-bonded interactions of TyrD and TyrD* with neighbouring D2His189 and D2Gln164. In the TyrD-state, an IR mode of formate significantly different from that observed in solution, is detected using 13C-formate, showing that formate forms a strong electrostatic interaction within PS II. The presence of formate affects also IR bands that may be assigned to an arginine side chain. Upon TyrD* formation, formate does not protonate but its binding interaction weakens. A proton uptake by Mes or phosphate buffer is detected, which is not observed when BisTris is used as a buffer. In these latter conditions, IR bands characteristic of the protonation of a carboxylate group of the protein are detected instead. The present IR data and the recent structural model of the TyrD environment proposed by Ferreira KN, Iverson TM, Maghlaoui K, Barber J and Iwata S [(2004) Science 303: 1831-1838], suggest that the proton released upon TyrD* formation is shared within a hydrogen bonding network including D2Arg294, and CP47Glu364 and that perturbation of this network by formate - possibly binding near D2Arg294 - substantially affects the properties of TyrD.
Hienerwadel
Rainer
R
Laboratoire de Génétique et de Biophysique des Plantes, Case 901, Faculté des Sciences de Luminy, UMR 6191 CNRS-CEA-Université Aix-Marseille II, Av. de Luminy, 13288 Marseille, Cedex, France. rhiener@luminy.univ-mrs.fr
Gourion-Arsiquaud
Samuel
S
Ballottari
Matteo
M
Bassi
Roberto
R
Diner
Bruce A
BA
Berthomieu
Catherine
C
D000595:Amino Acid Sequence; D005561:Formates / Q000737:chemistry / Q000378:metabolism*; D006860:Hydrogen Bonding; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared; D018724:Spinacia oleracea / Q000378:metabolism; D046939:Synechocystis / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry* / Q000378:metabolism*
D005561:Formates; D045332:Photosystem II Protein Complex; C030544:formic acid; D014443:Tyrosine