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Manganese-stabilizing protein of photosystem II, an intrinsically disordered polypeptide, contains a high ratio of charged to hydrophobic amino acid residues. Argl51 and Argl61 are conserved in all known MSP sequences. To examine the role of these basic residues in MSP structure and function, three mutants of spinach MSP, R151G, R151D, and R161G, were produced. Here, we present evidence that replacement of Arg151 or Arg161 yields proteins that have lower PSII binding affinity, and are functionally deficient even though about 2 tool of mutant MSP/mol PSII can be rebound to MSP depleted PSII membranes. R161G reconstitutes O2 evolution activity to 40% of the control, while R151G and R151D reconstitute only 20% of the control activity. Spectroscopic and biochemical techniques fail to detect significant changes in solution structure. More extensive 02 evolution assays revealed that the Mn cluster is stable in samples reconstituted with each mutated MSP, and that all three Arg mutants have the same ability to retain Ca2+ as the wild-type protein. Activity assays exploring the effect of these mutations on retention of CI-, however, showed that the R151 G, R I 51 D, and R 161G MSPs are defective in Cl- binding to the OEC. The mutants have Cl- KM values that are about four (R161G) or six times (R151G and R151D) higher than the value for the wild-type protein. The results reported here suggest that conserved positive charges on the manganese-stabilizing protein play a role in proper functional assembly of the protein into PSII, and, consequently, in retention of Cl- by the O2-evolving complex. [ABSTRACT FROM AUTHOR]

Examines the role of leucine 245 in the function and folding of the Manganese Stabilizing Protein (MSP) of photosystem II. Decrease in PSII binding affinity and oxygen evolution activity; Insignificance of glutamate 246 for MSP structure and function; Effects of mutations on MSP stability; Formation of prolate ellipsoid shape of MSP.

Focuses on the role of the carboxyl-terminal tripeptide of manganese-stabilizing protein in the quantitative assembly of the photosystem and oxygen evolution activity. Reference to studies conducted on the in vitro reconstitution of the spinach photosystem; Information on the photosynthetic oxygen evolution of plants.

Presents a study on isotope editing and vibrational spectroscopy, to obtain information about changes in secondary structure that occur in manganese stabilizing protein (MSP) upon functional reconstitution to photosystem II. Analysis of amide I band line shapes through Fourier deconvolution and nonlinear regression; Indication that binding of MSP to the reaction center can reduce folding of MSP; Indepth look at the study.

Investigates the effects of the mutation Val235Ala on the binding of the 33-kDa manganese stabilizing protein (MSP) of photosystem II to one of two sites. Role of MSP in the regulation and stabilization of oxygen gas evolution activity; Description of the cold-sensitive assembly of a mutant 33-kda protein with a single amino acid replacement.

Reports that photosystem II (PSII) is a multisubunit transmembrane protein complex that oxidizes water and evolves oxygen. Description of the experimental procedures; Cloning of spinach psbO; Purification and folding of MSP; Purification of PSII membranes; Reconstitution of PSII and measurement of O2 evolution.

Investigates the functional and structural consequences of N-terminal elongation and truncation of manganese stabilizing protein. Ability of the protein to reconstitute O&sub2; evolution activity; Exhibition of the protein of nonspecific binding; Influence of the N-terminal elongation and deletion of manganese stabilizing protein on conformation.