Water‐soluble 17 and 23 kDa polypeptides restore oxygen evolution activity by creating a high‐affinity binding site for Ca2+ on the oxidizing side of Photosystem II

FEBS Letters

Babcock, Gerald T.²  Topper, James N.¹  Yocum, Charles F.¹  Ghanotakis, Demetrios F.¹ 

[1]Division of Biological Sciences and Department of Chemistry, The University of Michigan, Ann Arbor, MI 48109-1048, USA

[2]Department of Chemistry, Michigan State University, East Lansing, MI 48824-1322, USA

关键词: Photosystem II;    Oxygen evolution;    Calcium;    Polypeptide;    Chl;    chlorophyll;    DCBQ;    2;    5-dichloro-p-benzoquinone;    Mes;    4-morpholineethanesulfonic acid;    PS;    photosystem;    OEC;    oxygen evolving complex;   

DOI  :  10.1016/0014-5793(84)81393-9

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Exposure of detergent-isolated preparations of the Photosystem II complex to 2 M NaCl releases water-soluble 17 and 23 kDa polypeptides; the inhibited rate of oxygen evolution activity is stimulated by addition of Ca²⁺ [(1984) FEBS Lett. 167, 127–130]. Reactivation of oxygen evolution activity by Ca²⁺ requires the presence of the ion in high (mM) non-physiological concentrations. Using a new dialysis-reconstitution procedure we have shown that rebinding of the 17 and 23 kDa polypeptides restores oxygen evolution activity only when the system has not been pretreated with EGTA. Removal of loosely-bound Ca²⁺ from the salt-extracted PS II complex and from the polypeptide solution, by dialysis against EGTA, blocks reconstitution of oxygen evolution activity even though the two polypeptides do rebind; restoration of Ca²⁺ to EGTA-treated systems, after rebinding of the 17 and 23 kDa polypeptides, results in a strong reconstitution of oxygen evolution activity. The effect of rebound 17 and 23 kDa polypeptides is to promote high affinity binding of Ca²⁺ to the reconstituted membrane.

【 授权许可】

Unknown