title: Amino acid residues that influence the binding of manganese or calcium to photosystem II. 2. The carboxy-terminal domain of the D1 polypeptide.
abstract: To identify amino acid residues that ligate the manganese and calcium ions of photosystem II or are otherwise crucial to water oxidation, site-directed mutations were constructed in the unicellular cyanobacterium Synechocystis sp. PCC 6803 at all conserved carboxylate and histidine residues in the carboxy-terminal domain of the D1 polypeptide. Mutants with impaired photoautotrophic growth or oxygen evolution were characterized in vivo by measuring changes in the yield of variable chlorophyll a fluorescence after a saturating flash or brief illumination given in the presence of an electron-transfer inhibitor or following each in a series of saturating flashes given in the absence of inhibitor [Chu, H.-A., Nguyen, A. P., & Debus, R.J. (1994) Biochemistry 33, 6137-6149]. Mutants were also characterized after propagation in media having other cations substituted for calcium. We conclude that His-332 Glu-333, His-337, and Asp-342 influence the assembly and/or stability of the manganese cluster, that His-332, Glu-333, and His-337 may ligate manganese, that Asp-342 may ligate manganese, calcium, or both, that Glu-333 and Asp-342 may play important structural roles, and that His-332, Glu-333, and His-337 influence the binding of calcium, although Glu-333 is unlikely to ligate Ca2+ directly. Several His-332, Glu-333, His-337, and Asp-342 mutants were very light sensitive, possibly because toxic activated oxygen species were released from altered or partly assembled manganese clusters. Finally, mutations at Asp-342 do not prevent posttranslational cleavage of the carboxy-terminal extension of the D1 polypeptide's precursor form in vivo.
authors.affiliation: Department of Biochemistry, University of California at Riverside 92521-0129, USA.
authors.forename: H A
authors.initials: HA
authors.lastname: Chu
authors.forename: A P
authors.initials: AP
authors.lastname: Nguyen
authors.forename: R J
authors.initials: RJ
authors.lastname: Debus
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D001224:Aspartic Acid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002734:Chlorophyll / Q000737:chemistry; D000077194:Chlorophyll A; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism; D004579:Electron Transport; D018698:Glutamic Acid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006639:Histidine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008345:Manganese / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010777:Photochemistry; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D010971:Plastoquinone / Q000378:metabolism; D013329:Structure-Activity Relationship; D014867:Water / Q000378:metabolism
chemical_list: D000596:Amino Acids; D045342:Light-Harvesting Protein Complexes; D010446:Peptide Fragments; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D014867:Water; D002734:Chlorophyll; D001224:Aspartic Acid; D018698:Glutamic Acid; D008345:Manganese; D006639:Histidine; D010971:Plastoquinone; D010100:Oxygen; D002118:Calcium; D000077194:Chlorophyll A