Protease treatments of photosystem II membrane fragments reveal that there are four separate high-affinity Mn-binding sites

Journal Article · Tue Oct 08 00:00:00 EDT 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00104a009· OSTI ID:5634313

Preston, C; Seibert, M ^[1]

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1. Solar Research Inst., Golden, CO (United States)

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.

• DOE Contract Number: AC02-83CH10093
• OSTI ID: 5634313
• Journal Information: Biochemistry; (United States), Vol. 30:40; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

14 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
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)