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Titolo:
COPPER(II) INHIBITION OF ELECTRON-TRANSFER THROUGH PHOTOSYSTEM-II STUDIED BY EPR SPECTROSCOPY
Autore:
JEGERSCHOLD C; ARELLANO JB; SCHRODER WP; VANKAN PJM; BARON M; STYRING S;
Indirizzi:
UNIV STOCKHOLM,ARRHENIUS LAB,DEPT BIOCHEM S-10691 STOCKHOLM SWEDEN UNIV STOCKHOLM,ARRHENIUS LAB,DEPT BIOCHEM S-10691 STOCKHOLM SWEDEN CSIC,DEPT BIOCHEM CELL & MOLEC BIOL PLANTS,ESTAC EXPTL ZAIDIN E-18008GRANADA SPAIN
Titolo Testata:
Biochemistry
fascicolo: 39, volume: 34, anno: 1995,
pagine: 12747 - 12754
SICI:
0006-2960(1995)34:39<12747:CIOETP>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
PHOTOSYNTHETIC OXYGEN EVOLUTION; CU(II)-INHIBITORY BINDING-SITE; PARAMAGNETIC-RES MEASUREMENTS; REACTION CENTERS; SPINACH-CHLOROPLASTS; THYLAKOID MEMBRANES; QUINONE ACCEPTOR; HIGHER-PLANT; TRANSPORT; CALCIUM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
57
Recensione:
Indirizzi per estratti:
Citazione:
C. Jegerschold et al., "COPPER(II) INHIBITION OF ELECTRON-TRANSFER THROUGH PHOTOSYSTEM-II STUDIED BY EPR SPECTROSCOPY", Biochemistry, 34(39), 1995, pp. 12747-12754

Abstract

EPR spectroscopy was applied to investigate the inhibition of electron transport in photosystem II by Cu2+ ions. Our results show that Cu2has inhibitory effects on both the donor and the acceptor side of photosystem II. In the presence of Cu2+, neither EPR signal IIvery (fast)nor signal IIfast, which both reflect oxidation of tyrosine(Z), couldbe induced by illumination. This shows that Cu2+ inhibits electron transfer from tyrosine(Z) to the oxidized primary donor P680(+). Insteadof tyrosine(Z) oxidation, illumination results in the formation of a new radical with g = 2.0028 +/- 0.0002 and a spectral width of 9.5 +/-0.3 G. At room temperature, this radical amounts to one spin per PS IT reaction center. Incubation of photosystem II membranes with cupric ions also results in release of the 16 kDa extrinsic subunit and conversion of cytochrome b(559) to the low-potential form. On the acceptor side, QA can still be reduced by illumination or chemical reduction with dithionite. However, incubation with Cu2+ results in loss of the normal EPR signal from Q(A)(-) which is coupled to the non-heme Fe2+ on the acceptor side (the Q(A)(-)-Fe2+ EPR signal). Instead, reduction ofQA results in the formation of a free radical spectrum which is 9.5 Gwide and centered at g = 2.0044. This signal is attributed to Q(A)(-)which is magnetically decoupled from the nonheme iron. This suggests that Cu2+ displaces the Fe2+ or severly alters its binding properties. The inhibition of tyrosine(Z) is reversible upon removal of the copper ions with EDTA while the modification of Q(A) was found to be irreversible.

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Documento generato il 24/11/20 alle ore 14:13:49