Kinetic and cross-linking studies on the interactions of negative patch mutant plastocyanin from Silene pratensis with photosystem I complexes from cyanobacteria, green algae, and plants.
The site-directed mutants of negative patches on silene plastocyanin (PC) were used to investigate the change of interactions between photosystem I (PSI) and PC during the course of evolution from cyanobacteria to plants. The net charges of two highly conserved negative patches (#42-45 and #59-61) on silene PC were systematically modified from -4 to +1. PSI complexes from cucumber and Chlamydomonas reinhardtii were efficient electron acceptors for silene PC. The increase of net charge on the negative patch (#42-45) of silene PC decreased the reduction rates of PSI from cucumber and Chlamydomonas, while the modification of the other negative patch (#59-61) had no effect. Though the addition of MgCl2 decreased the reduction rate of cucumber PSI, the decrease was severely diminished in the case of Chlamydomonas PSI, and the reduction rate increased with increasing concentration of MgCl2 when the net charge of the negative patch (#42-45) was modified to +1. The PSI complexes from Anabaena variabilis and Synechosystis sp. PCC 6803 were inefficient electron acceptors for silene PC and their rates were almost independent of the net charge of the negative patches, as well as the ionic strength of the reaction mixtures. Silene PC specifically cross-linked to the PsaF subunit of PSI complexes from cucumber, Chlamydomonas, Anabaena, and Synechosystis sp. PCC 6803. Modification of the negative patch (#42-45) inhibited the formation of cross-linked adducts in all the cases examined, whereas modification of the other negative patch (#59-61) had essentially no effect. Based on these results, the changes of electrostatic interactions between PC and PSI during the course of evolution from cyanobacteria to plants are discussed.
Department of Chemistry, Faculty of Science & Technology, Meijo University, Nagoya.
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Hibino
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Lee
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Yajima
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Odani
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Yamauchi
T
T
Takabe
D000595:Amino Acid Sequence; D017033:Anabaena / Q000378:metabolism*; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D003432:Cross-Linking Reagents; D000458:Cyanobacteria / Q000378:metabolism*; D005022:Ethyldimethylaminopropyl Carbodiimide; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009994:Osmolar Concentration; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D045331:Photosystem I Protein Complex; D010944:Plants / Q000378:metabolism*; D010970:Plastocyanin / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D003432:Cross-Linking Reagents; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D011994:Recombinant Proteins; D010970:Plastocyanin; D005022:Ethyldimethylaminopropyl Carbodiimide