Protective role of CaCl2 against Pb2+ inhibition in photosystem II

FEBS Letters

Popovic, Radovan¹  Rashid, Abdur¹ 

[1] Département de chimie, Université du Québec à Montréal, Case postale 8888, Succ. ‘A’, Montréal, Québec, H3C 3P8, Canada

关键词: Photosystem II;    Lead inhibition;    Calcium chloride;    Oxygen evolution;    Electron transport;    Extrinsic polypeptide;    Variable fluorescence;    DCIP;    2;    6-dichlorophenolindophenol;    Mes;    2-(N-morpholine)ethanesulfonic acid;    DPC;    diphenylcarbazide;    DCBQ;    2;    5-dichlorobenzoquinone;    WSC;    water-splitting complex;    Chi;    chlorophyll;    PS;    photosystem;   

DOI  :  10.1016/0014-5793(90)80401-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The Pb²⁺ treatment of Photosystem II (PS II) membrane fragments, either intact or depleted in 17 and 23 kDa extrinsic polypeptides, inhibits PS II activity. When CaCl₂ was present in the assay, the Pb²⁺ inhibition was significantly reduced in both types of PS II membranes, suggesting a protective role of CaCl₂ against Pb²⁺ inhibition. However, in either case, the degree of PS II inhibition by Pb²⁺ was higher in the protein depleted than in intact PS II. It showed that the loss of endogenous Ca²⁺ induced by polypeptide depletion causes the PS II to be more susceptible to Pb²⁺. The interaction of Pb²⁺ with CaCl₂ in protein-depleted PS II was competitive. Our results suggest that Pb²⁺ competes for binding to the Ca²⁺ and Cl⁻ active sites in the water-splitting complex. Since Pb²⁺ inhibition of PS II activity cannot be reversed by CaCl₂ but can be reversed by diphenylcarbazide, we conclude that Pb²⁺ induced inhibition of PS II activity was mediated via the water-splitting system.

【 授权许可】

Unknown