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Titolo:
2 FUNCTIONALLY DISTINCT FORMS OF THE PHOTOSYSTEM-II REACTION-CENTER PROTEIN D1 IN THE CYANOBACTERIUM SYNECHOCOCCUS SP PCC 7942
Autore:
CLARKE AK; HURRY VM; GUSTAFSSON P; OQUIST G;
Indirizzi:
UMEA UNIV,DEPT PLANT PHYSIOL S-90187 UMEA SWEDEN
Titolo Testata:
Proceedings of the National Academy of Sciences of the United Statesof America
fascicolo: 24, volume: 90, anno: 1993,
pagine: 11985 - 11989
SICI:
0027-8424(1993)90:24<11985:2FDFOT>2.0.ZU;2-W
Fonte:
ISI
Lingua:
ENG
Soggetto:
PSBA GENE FAMILY; CHLOROPHYLL FLUORESCENCE; ANACYSTIS-NIDULANS; LIGHT-INTENSITY; PHOTOINHIBITION; PHOTOSYNTHESIS; DEGRADATION; EXPRESSION; IDENTIFICATION; THYLAKOIDS;
Keywords:
CHLOROPHYLL FLUORESCENCE; PHOTOSYNTHESIS; PROTEIN TURNOVER;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
27
Recensione:
Indirizzi per estratti:
Citazione:
A.K. Clarke et al., "2 FUNCTIONALLY DISTINCT FORMS OF THE PHOTOSYSTEM-II REACTION-CENTER PROTEIN D1 IN THE CYANOBACTERIUM SYNECHOCOCCUS SP PCC 7942", Proceedings of the National Academy of Sciences of the United Statesof America, 90(24), 1993, pp. 11985-11989

Abstract

The cyanobacterium Synechococcus sp. PCC 7942 possesses a small psbA multigene family that codes for two distinct forms of the photosystem II reaction-center protein D1 (D1:1 and D1:2). We showed previously that the normally predominant D1 form (D1:1) was rapidly replaced with the alternative D1:2 when cells adapted to a photon irradiance of 50 mumol/m-2.s-1 are shifted to 500 mumol.m-2.s-1 and that this interchangewas readily reversible once cells were allowed to recover under the original growth conditions. By using the psbA inactivation mutants R2S2C3 and R2K1 (which synthesize only D1:1 and D1:2, respectively), we showed that this interchange between D1 forms was essential for limitingthe degree of photoinhibition as well as enabling a rapid recovery ofphotosynthesis. In this report, we have extended these findings by examining whether any intrinsic functional differences exist between thetwo D1 forms that may afford increased resistance to photoinhibition. Initial studies on the rate of D1 degradation at three photon-irradiances (50, 200, and 500 mumol.m-2.s-1) showed that the rates of degradation for both D1 forms increase with increasing photon flux density but that there was no significant difference between D1:1 and D1:2. Analysis of light-response curves for oxygen evolution for the mutants R2S2C3 and R2K1 revealed that cells with photosystem II reaction centers containing D1:2 have a higher apparent quantum yield (almost-equal-to 25%) than cells possessing D1:1. Further studies using chlorophyll a fluorescence measurements confirmed that R2K1 has a higher photochemical yield than R2S2C3; that is, a more efficient conversion of excitation energy from photon absorption into photochemistry. We believe that the higher photochemical efficiency of reaction centers containing D1:2is causally related to the preferential induction of D1:2 at high light and thus may be an integral component of the protection mechanism within Synechococcus sp. PCC 7942 against photoinhibition.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 28/11/20 alle ore 12:15:22