Function of the 23 kDa extrinsic protein of Photosystem II as a manganese binding protein and its role in photoactivation

Biochim Biophys Acta. 2005 Jun 1;1708(1):63-70. doi: 10.1016/j.bbabio.2005.01.005. Epub 2005 Jan 27.


The function of the extrinsic 23 kDa protein of Photosystem II (PSII) was studied with respect to Mn binding and its ability to supply Mn to PSII during photoactivation, i.e. the light-dependent assembly of the tetramanganese cluster. The extrinsic proteins and the Mn cluster were removed by TRIS treatment from PSII-enriched membrane fragments and purified by anion exchange chromatography. Room temperature EPR spectra of the purified 23 kDa protein demonstrated the presence of Mn. Photoactivation was successful with low Mn concentrations when the 23 kDa protein was present, while in its absence a higher Mn concentration was needed to reach the same level of oxygen evolution activity. In addition, the rate of photoactivation was significantly accelerated in the presence of the 23 kDa protein. It is proposed that the 23 kDa protein plays an important role in providing Mn during the process of PSII assembly and that it acquires Mn during the light-induced turnover of D1 in the PSII damage-repair cycle and delivers Mn to repaired PSII.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carrier Proteins / metabolism*
  • Electron Spin Resonance Spectroscopy
  • Electrophoresis, Polyacrylamide Gel
  • Light
  • Manganese / metabolism*
  • Photosynthetic Reaction Center Complex Proteins / physiology*
  • Photosynthetic Reaction Center Complex Proteins / radiation effects
  • Photosystem II Protein Complex / physiology*
  • Photosystem II Protein Complex / radiation effects
  • Plant Proteins / physiology*
  • Plant Proteins / radiation effects
  • Spinacia oleracea / metabolism
  • Spinacia oleracea / ultrastructure


  • Carrier Proteins
  • Photosynthetic Reaction Center Complex Proteins
  • Photosystem II Protein Complex
  • Plant Proteins
  • Manganese