Characterization of a redox-active cross-linked complex between cyanobacterial photosystem I and its physiological acceptor flavodoxin

被引:39
作者
Muhlenhoff, U
Kruip, J
Bryant, DA
Rogner, M
Setif, P
Boekema, E
机构
[1] UNIV MUNSTER, INST BOT, D-48149 MUNSTER, GERMANY
[2] PENN STATE UNIV, DEPT BIOCHEM & MOLEC BIOL, UNIVERSITY PK, PA 16802 USA
[3] CTR ETUD SACLAY, DEPT BIOL CELLULAIRE & MOLEC, CEA, F-91191 GIF SUR YVETTE, FRANCE
[4] UNIV GRONINGEN, 9747 AG GRONINGEN, NETHERLANDS
关键词
cyanobacteria; electronmicroscopy; flavodoxin; photosystem I; spectroscopy;
D O I
10.1002/j.1460-2075.1996.tb00381.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
A covalent complex between photosystem I and flavodoxin from the cyanobacterium Synechococcus sp, PCC 7002 was generated by chemical cross-linking, Laser flash-absorption spectroscopy indicates that the bound flavodoxin of this complex is stabilized in the semiquinone state and is photoreduced to the quinol form upon light excitation. The kinetics of this photoreduction process, which takes place in similar to 50% of the reaction centres, displays three exponential components with half-lives of 9 mu s, 70 mu s and 1 ms. The fully reduced flavodoxin subsequently recombines with P700(+) with a t(1/2) of 330 ms. A corresponding flavodoxin semiquinone radical signal is readily observed in the dark by room temperature electron paramagnetic resonance, which reversibly disappears upon illumination. In contrast, the light-induced reduction of oxidized flavodoxin can be observed only by first-flash experiments following excessive dark adaptation. In addition, the docking site of flavodoxin on photosystem I was determined by electron microscopy in combination with image analysis, Flavodoxin binds to the cytoplasmic side of photosystem I at a distance of 7 nm from the centre of the trimer and in close contact to a ridge formed by the subunits PsaC, PsaD and PsaE.
引用
收藏
页码:488 / 497
页数:10
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