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Author Preston, C. ♦ Seibert, M.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword SOLAR ENERGY ♦ PEPTIDE HYDROLASES ♦ BIOCHEMICAL REACTION KINETICS ♦ PHOTOSYNTHETIC REACTION CENTERS ♦ MOLECULAR BIOLOGY ♦ CARBAZIDES ♦ LIGANDS ♦ MANGANESE COMPOUNDS ♦ PHOTOSYNTHESIS ♦ PHOTOSYNTHETIC MEMBRANES ♦ CARBONIC ACID DERIVATIVES ♦ CHEMICAL REACTIONS ♦ ENZYMES ♦ HYDROLASES ♦ KINETICS ♦ MEMBRANES ♦ ORGANIC COMPOUNDS ♦ ORGANIC NITROGEN COMPOUNDS ♦ PHOTOCHEMICAL REACTIONS ♦ PROTEINS ♦ REACTION KINETICS ♦ SYNTHESIS ♦ TRANSITION ELEMENT COMPOUNDS ♦ Solar Energy Conversion- Photochemical, Photobiological, & Thermochemical Conversion- (1980-)
Abstract The high-affinity Mn-binding site in Mn-depleted photosystem II (PS II) membrane fragments isolated from Scenedesmus obliquus was examined by using the diphenylcarbazide (DPC)/Mn{sup 2+} noncompetitive inhibition assay. Different proteases were used to degrade lumenal surface protein segments from these PS II membranes, and a total of four independent high-affinity Mn-binding sites (ligands) were identified. Carboxypeptidase A, subtilisin, and Staphylococcus aureus V8 protease each degrade one of two high-affinity Mn-binding sites sensitive to the histidine chemical modifier diethyl pyrocarbonate (DEPC). However, sequential treatment experiments indicate that subtilisin degrades a DEPC-sensitive Mn-binding site that is different from the one degraded by the other two proteases. Trypsin also was found to degrade one of the DEPC-sensitive Mn-binding sites. These four high-affinity Mn-binding sites may correspond to the four sites formed, albeit sequentially, in the normal photoactivation process. The authors provide evidence that a histidine residue (His 337) on D1 is a prime candidate for one of the high-affinity Mn-binding sites and suggest that it also provides a nitrogen ligand for binding functional Mn. Finally, an alternative explanation of our data might be that the four high-affinity sites represent four ligands binding a single Mn, and ligands to other membrane bound Mn are not detectable by the DPC/Mn{sup 2+} assay.
ISSN 00062960
Educational Use Research
Learning Resource Type Article
Publisher Date 1991-10-08
Publisher Place United States
Journal Biochemistry
Volume Number 30
Issue Number 40


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