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CaCl 2 inhibition of H 2 O 2 electron donation to photosystem II in submembrane preparations depleted in extrinsic polypeptides
Author(s) -
Rashid Abdur,
Carpentier Robert
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)81686-2
Subject(s) - photosystem ii , chemistry , kinetics , p680 , oxygen evolution , oxygen , oxygen evolving complex , dcmu , biophysics , photosynthesis , photochemistry , nuclear chemistry , biochemistry , photosystem i , biology , physics , organic chemistry , electrode , quantum mechanics , electrochemistry
The interaction of CaCl 2 , and H 2 O 2 , was studied in photosystem II (PSII) enriched submembrane preparations depleted in the extrinsic polypeptides associated with oxygen evolution. In PSII preparations, depleted of 16 and 23 kDa polypeptides, the addition of exogenous CaCl 2 ; substantially stimulated the rate of H 2 O oxidation but had no effect on the rate of H 2 O 2 ; oxidation. In PSII preparations depleted of 16, 23 and 33 kDa polypeptides, addition of CaCl 2 , strongly inhibited the H 2 O 2 , oxidation when mediated via exogenous Mn 2+ . The inhibition kinetics of H 2 O 2 , oxidation by CaCl 2 ; in these PSII preparations were negatively correlated with the retention of native Mn‐atoms in the PSII core complex. These results suggest that removal of 16 and 23 kDa extrinsic polypeptides from the PSII oxygen‐evolving complex causes disorganisation of Ca 2+ and Cl − and allows H 2 O 2 , to undergo oxidation and to donate electrons to P680 via the native Mn‐cluster and/or exogenous Mn 2+ . However, readdition of Ca 2+ and Cl − to the depleted preparations restores the native conformation of the PSII core complex, consequently inhibiting H 2 O 2 ; oxidation.