Lack of Photoactivation Capacity in Scenedesmus Obliquus LF-1 Results from Loss of Half the High-Affinity Manganese-Building Site. Relationship to the Unprocessed D1 Protein

Michael Seibert, Noriaki Tamura, Yorinao Inoue

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66 Scopus Citations

Abstract

The high-affinity binding site for Mn2+ is characterized by a decrease in 1,5-diphenylcarbazide (DPC) to 2,6-dichlorophenolindophenol (DCIP) electron transport with NH2OH-treated spinach Photosystem II (PS II) membrane fragments when micromolar amounts of Mn2+ are present in the assay. This site is purported to be the binding site for Mn, functional in O2 evolution (Hsu, B.-D., Lee, J.-Y. and Pan, R.-L. (1987) Biochim. Biophys. Acta 890, 89-96). We have examined this site in PS II-enriched membranes from Scenedesmus obliquus wild-type (WT) and LF-1 mutant cells. LF-1 inserts an unprocessed D1 protein into the photosynthetic membrane, binds approx. 40% of the functional Mn as WT, and does not evolve O2 (Metz, J.G., Pakrasi, H.B., Seibert, M. and Arntzen, C.J. (1986) FEBS Lett. 205, 269-274). The dissociation constant for added high-affinity Mn2+ is about 0.3-0.4 μM in wheat, WT, and LF-1 PS II. However, the relative amount of available high-affinity Mn2+-binding site is about half as much in LF-1 PS II membranes compared to wheat, spinach, and WT PS II membranes. Despite the fact that LF-1 PS II can photoligate Mn, LF-1 cannot be photoactivateid as can NH2OH-treated WT PS II. LF-1 subjected to photoactivating conditions does not reach S2 as determined by thermoluminescence. This work indicates that the Hsu et al. high-affinity Mn2+ site is actually at least two sites, one of which is missing in LF-1, and that successful photoactivation potential requires the presence of all high-affinity Mn2+ site. The fact that the full complement of high-affinity Mn2+-binding site is observed in isolated spinach PS II reaction center (D1/D2/cytochrome b-559) complex demonstrates that other PS II core proteins do not affect the high-affinity site. Histidine chemical modifier experiments show that one component of the high-affinity site is probably associated with histidine(s) and that this component is missing in LF-1. We conclude that histidine(s) on the Dl protein provides ligand(s) for part of the Mn required for O2-evolution function and that the balance of the Mn is bound by other amino acids on the proteins composing the PS II reaction center.

Original languageAmerican English
Pages (from-to)185-191
Number of pages7
JournalBBA - Bioenergetics
Volume974
Issue number2
DOIs
StatePublished - May 1989

Bibliographical note

Work performed by Solar Energy Research Institute, Golden, Colorado, and Solar Energy Group and Frontier Research Group, Institute of Physical and Chemical Research, Saitama, Japan

NREL Publication Number

  • ACNR/JA-233-11348

Keywords

  • D1 protein
  • Histidine
  • Manganese
  • Oxygen evolution
  • Photosynthesis
  • Scenedesmus mutant (LF-1)

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