Interaction of Zn2+with the donor side of Photosystem II

✍ Scribed by Abdur Rashid; Michelle Bernier; Leroy Pazdernick; Robert Carpentier

• Publisher: Springer
• Year: 1991
• Tongue: English
• Weight: 601 KB
• Volume: 30
• Category: Article
• ISSN: 0166-8595
• DOI: 10.1007/bf00042010

✦ Synopsis

The inhibitory effect of Zn 2+ on photosynthetic electron transport was investigated in native and CaC12-treated (depleted in extrinsic polypeptides) Photosystem II (PS II) submembrane preparations. Inhibition of 2,6-dichlorophenolindophenol photoreduction by Zn 2+ was much stronger in proteindepleted preparations in comparison to the native form. It was found that Ca 2+ significantly reduced the inhibition in the native PS II preparations, as did Mn 2+ in a combination with H20 2 in the proteindepleted counterparts. No other tested monovalent or divalent cations could replace Ca 2+ or Mn 2+ in the respective experiments. Diphenylcarbazide could partially relieve (40-45%) the inhibition in both types of preparations. The above indicates the presence of an active Zn 2+ inhibitory site on the donor side of PS II. However, neither Ca 2+ nor Mn 2+ could completely prevent inhibition by high concentrations of Zn 2+ (>1 mM). We propose that elevated levels of Zn 2+ strongly perturb the conformation of the PS II core complex and might also affect the acceptor side of the photosystem.