Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
REACTIONS OF ISOCYTOCHROME C(2) IN THE PHOTOSYNTHETIC ELECTRON-TRANSFER CHAIN OF RHODOBACTER-SPHAEROIDES
Autore:
WITTHUHN VC; GAO JL; HONG SJ; HALLS S; ROTT MA; WRAIGHT CA; CROFTS AR; DONOHUE TJ;
Indirizzi:
UNIV WISCONSIN,DEPT BACTERIOL MADISON WI 53706 UNIV WISCONSIN,DEPT BACTERIOL MADISON WI 53706 UNIV ILLINOIS,DEPT PLANT BIOL URBANA IL 61801 UNIV ILLINOIS,CTR BIOPHYS & COMPUTAT BIOL URBANA IL 61801
Titolo Testata:
Biochemistry
fascicolo: 4, volume: 36, anno: 1997,
pagine: 903 - 911
SICI:
0006-2960(1997)36:4<903:ROICIT>2.0.ZU;2-0
Fonte:
ISI
Lingua:
ENG
Soggetto:
PHOTOOXIDIZED BACTERIOCHLOROPHYLL DIMER; CYTOCHROME-C(2) MEDIATED REREDUCTION; SITE-DIRECTED MUTAGENESIS; L-SUBUNIT PLAYS; REACTION CENTERS; RHODOPSEUDOMONAS-SPHAEROIDES; RHODOSPIRILLUM-RUBRUM; PHOSPHOLIPID-VESICLES; PHOTO-OXIDATION; PRIMARY DONOR;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
56
Recensione:
Indirizzi per estratti:
Citazione:
V.C. Witthuhn et al., "REACTIONS OF ISOCYTOCHROME C(2) IN THE PHOTOSYNTHETIC ELECTRON-TRANSFER CHAIN OF RHODOBACTER-SPHAEROIDES", Biochemistry, 36(4), 1997, pp. 903-911

Abstract

Rhodobacter sphaeroides strains lacking cytochrome c(2) (cyt c(2)), the normal electron donor to P-870(+) in light-oxidized reaction center(RC) complexes, are unable to grow photosynthetically. However, spd mutations that suppress the photosynthetic deficiency of cyt ct mutantselevate levels of the cyt c(2) isoform, isocyt c(2). We monitored photosynthetic electron transfer in whole cells, in chromatophores, and with purified components to ascertain if and how isocyt c(2) reduced light-oxidized RC complexes. These studies revealed that several fundamental aspects of photosynthetic electron transfer were similar in strains that use isocyt c(2) and wild-type cells. For example, P-870(+) reduction accompanied cytochrome c oxidation. In addition, photosyntheticelectron transfer was blocked by the well-known cyt bc(1) complex inhibitors antimycin and myxothiazol. However, even at the increased isocyt c(2) levels present in these strains (similar to 40% that of cyt c(2) in wild-type cells), there was little, if any, of the rapid (<5 mu s) electron transfer to P-870(+) that is characteristic of cytochromesbound to RC complexes at the time of the light flash. Thus, it appears that isocyt c(2) function limits the in vivo rate of P-870(+) reduction. Indeed, at low ionic strength in vitro, the apparent affinity of isocyt c(2) for RC complexes (K-D similar to 40 mu M) is significantlylower than that of cyt c(2) (K-D similar to 1.0 mu M). This reduced affinity does not appear to result from an altered mode of RC binding by isocyt c(2) since electrostatic interactions make similar overall contributions to the binding of both cyt c(2) and isocyt c(2) to this membrane-bound redox partner. Thus, sequence, structural, or local conformational differences between cyt c(2) and isocyt c(2) significantly alter their apparent affinities for this physiologically relevant redoxpartner.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 05/07/20 alle ore 13:19:30