PubMed:10722691 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PubMed/sourceid/10722691","sourcedb":"PubMed","sourceid":"10722691","source_url":"http://www.ncbi.nlm.nih.gov/pubmed/10722691","text":"Recruitment of a foreign quinone into the A(1) site of photosystem I. II. Structural and functional characterization of phylloquinone biosynthetic pathway mutants by electron paramagnetic resonance and electron-nuclear double resonance spectroscopy.\nElectron paramagnetic resonance (EPR) and electron-nuclear double resonance studies of the photosystem (PS) I quinone acceptor, A(1), in phylloquinone biosynthetic pathway mutants are described. Room temperature continuous wave EPR measurements at X-band of whole cells of menA and menB interruption mutants show a transient reduction and oxidation of an organic radical with a g-value and anisotropy characteristic of a quinone. In PS I complexes, the continuous wave EPR spectrum of the photoaccumulated Q(-) radical, measured at Q-band, and the electron spin-polarized transient EPR spectra of the radical pair P700(+) Q(-), measured at X-, Q-, and W-bands, show three prominent features: (i) Q(-) has a larger g-anisotropy than native phylloquinone, (ii) Q(-) does not display the prominent methyl hyperfine couplings attributed to the 2-methyl group of phylloquinone, and (iii) the orientation of Q(-) in the A(1) site as derived from the spin polarization is that of native phylloquinone in the wild type. Electron spin echo modulation experiments on P700(+) Q(-) show that the dipolar coupling in the radical pair is the same as in native PS I, i.e. the distance between P700(+) and Q(-) (25.3 +/- 0.3 A) is the same as between P700(+) and A(1)(-) in the wild type. Pulsed electron-nuclear double resonance studies show two sets of resolved spectral features with nearly axially symmetric hyperfine couplings. They are tentatively assigned to the two methyl groups of the recruited plastoquinone-9, and their difference indicates a strong inequivalence among the two groups when in the A(1) site. These results show that Q (i) functions in accepting an electron from A(0)(-) and in passing the electron forward to the iron-sulfur clusters, (ii) occupies the A(1) site with an orientation similar to that of phylloquinone in the wild type, and (iii) has spectroscopic properties consistent with its identity as plastoquinone-9.","tracks":[{"project":"sentences","denotations":[{"id":"T1","span":{"begin":0,"end":69},"obj":"Sentence"},{"id":"T2","span":{"begin":70,"end":73},"obj":"Sentence"},{"id":"T3","span":{"begin":74,"end":249},"obj":"Sentence"},{"id":"T4","span":{"begin":250,"end":444},"obj":"Sentence"},{"id":"T5","span":{"begin":445,"end":679},"obj":"Sentence"},{"id":"T6","span":{"begin":680,"end":1261},"obj":"Sentence"},{"id":"T7","span":{"begin":1262,"end":1522},"obj":"Sentence"},{"id":"T8","span":{"begin":1523,"end":1666},"obj":"Sentence"},{"id":"T9","span":{"begin":1667,"end":1853},"obj":"Sentence"},{"id":"T10","span":{"begin":1854,"end":2183},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"attributes":[{"subj":"T1","pred":"source","obj":"sentences"},{"subj":"T2","pred":"source","obj":"sentences"},{"subj":"T3","pred":"source","obj":"sentences"},{"subj":"T4","pred":"source","obj":"sentences"},{"subj":"T5","pred":"source","obj":"sentences"},{"subj":"T6","pred":"source","obj":"sentences"},{"subj":"T7","pred":"source","obj":"sentences"},{"subj":"T8","pred":"source","obj":"sentences"},{"subj":"T9","pred":"source","obj":"sentences"},{"subj":"T10","pred":"source","obj":"sentences"}]},{"project":"NCBITAXON","denotations":[{"id":"T1","span":{"begin":922,"end":931},"obj":"OrganismTaxon"},{"id":"T2","span":{"begin":1035,"end":1044},"obj":"OrganismTaxon"},{"id":"T3","span":{"begin":1276,"end":1280},"obj":"OrganismTaxon"}],"attributes":[{"id":"A1","pred":"db_id","subj":"T1","obj":"37571"},{"id":"A2","pred":"db_id","subj":"T2","obj":"37571"},{"id":"A3","pred":"db_id","subj":"T3","obj":"62031"},{"subj":"T1","pred":"source","obj":"NCBITAXON"},{"subj":"T2","pred":"source","obj":"NCBITAXON"},{"subj":"T3","pred":"source","obj":"NCBITAXON"}]},{"project":"CL-cell","denotations":[{"id":"T1","span":{"begin":500,"end":504},"obj":"Cell"},{"id":"T2","span":{"begin":784,"end":788},"obj":"Cell"}],"attributes":[{"id":"A1","pred":"cl_id","subj":"T1","obj":"http://purl.obolibrary.org/obo/CL:0000560"},{"id":"A2","pred":"cl_id","subj":"T2","obj":"http://purl.obolibrary.org/obo/CL:0000560"},{"subj":"T1","pred":"source","obj":"CL-cell"},{"subj":"T2","pred":"source","obj":"CL-cell"}]}],"config":{"attribute types":[{"pred":"source","value type":"selection","values":[{"id":"sentences","color":"#93ece3","default":true},{"id":"NCBITAXON","color":"#ecc993"},{"id":"CL-cell","color":"#af93ec"}]}]}}