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1997 (1)
1991 (1)
1Author    Bengt Svensson, Imre Vass, Stenbjörn StyringRequires cookie*
 Title    Sequence Analysis of the D 1 and D 2 Reaction Center Proteins of Photosystem II  
 Abstract    A com pilation o f 38 sequences for the D1 and 15 sequences for the D 2 reaction center pro­ teins o f photosystem II is presented. The sequences have been compared and a similarity index that takes into account the degree o f conservation and the quality o f the changes in each posi­ tion has been calculated. The similarity index is used to identify and describe functionally im­ portant domains in the D 1 /D 2 heterodimer. Comparative hydropathy plot are presented for the aminoacid sidechains that constitute the binding domain o f the tyrosine radicals, Tyrz and TyrD, in photosystem II. The structure around Tyrz is more hydrophilic than the structure around TyrD. The hydrophilic residues are clustered in the part o f the binding pocket for Tyrz that is turned towards the lumenal side o f the thylakoid membrane. M ost prominent is the presence o f two conserved carboxylic am inoacids, D l-A sp 170 and D l-G lu 189. Their respec­ tive carboxyl-groups com e close in space and are proposed to constitute a metal binding site together with D l-G ln 165. The distance between the proposed metal binding site and the cen­ ter o f the ring o f Tyrz is approximately 7Ä . The cavity that constitutes the binding site for TyrD is com posed o f residues from the D 2 protein. Its character is more hydrophobic than the Tyrz site and the environment around TyrD lacks the cluster o f putative metal binding side­ chains. 
  Reference    Z. Naturforsch. 46c, 765 (1991); received March 13 1991 
  Published    1991 
  Keywords    Photosystem II, D1 Protein, D 2 Protein, Tyrosine, M anganese, Reaction Center 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0765.pdf 
 Identifier    ZNC-1991-46c-0765 
 Volume    46 
2Author    Britta Förster3, PeterB. Heifetz0, Anita Lardansd, JohnE. Boyntona, NicholasW. GillhambRequires cookie*
 Title    Herbicide Resistance and Growth of D1 Ala25i Mutants in Chlamydomonas  
 Abstract    We elucidated the effects of substituting seven amino acids for Ala at residue 251 of the Chlam ydom onas reinhardtii D1 protein on herbicide resistance and photoautotrophic growth. A la25i has been suggested to play a key role in the structural integrity and function of the stromal loop between transmembrane helices IV and V of D1 and has previously been shown to affect resistance to "classical" PSII specific herbicides. Sensitive and rapid microtiter assays were employed to compare herbicide resistance and photoautotrophic growth in the various mutants. Substitution of Ala25i by Ile, Leu or Val conferred resistance to the PSII herbicides atrazine, bromacil and metribuzin but not to DCMU, and impaired photoautotrophic growth in high and low light. Compared to an otherwise isogenic wildtype strain, the lie and Val mutants exhibited nearly identical levels of herbicide resistance and reduced growth while the Leu mutant had even slower growth and higher levels of herbicide resistance. In contrast Cys, Pro, Ser and Gly mutants were phenotypically indistinguishable from wildtype in terms of herbicide sensitivity and photoautotrophic doubling times. Collectively the seven A la251 mutations differed markedly from an Ala mutant (dr-1) at the well characterized Ser264 D1 residue in terms of herbicide resistance and photoautotrophic growth. 
  Reference    Z. Naturforsch. 52c, 654—664 (1997); received June ll/Ju ly 2 1997 
  Published    1997 
  Keywords    D1 Protein, Site-Directed Chloroplast Mutations, Herbicide Resistance, Photoautotrophic Growth, Microtiter Assay 
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 TEI-XML for    default:Reihe_C/52/ZNC-1997-52c-0654.pdf 
 Identifier    ZNC-1997-52c-0654 
 Volume    52