Anabaena Flavodoxin as an Electron Carrier from Photosystem I to Ferredoxin-NADP+ Reductase. Role of Flavodoxin Residues in Protein-Protein Interaction and Electron Transfer
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- 作者：Isabel Nogué ; s ; Manuel Hervá ; s ; José ; R. Peregrina ; José ; A. Navarro ; Miguel A. de la Rosa ; Carlos Gó ; mez-Moreno ; and Milagros Medina
- 刊名：Biochemistry
- 出版年：2005
- 出版时间：January 11, 2005
- 年：2005
- 卷：44
- 期：1
- 页码：97 - 104
- 全文大小：327K
- 年卷期：v.44,no.1(January 11, 2005)
- ISSN：1520-4995
文摘
Biochemical and structural studies indicate that electrostatic and hydrophobic interactions arecritical in the formation of optimal complexes for efficient electron transfer (ET) between ferredoxin-NADP+ reductase (FNR) and ferredoxin (Fd). Moreover, it has been shown that several charged andhydrophobic residues on the FNR surface are also critical for the interaction with flavodoxin (Fld), although,so far, no key residue on the Fld surface has been found to be the counterpart of such FNR side chains.In this study, negatively charged side chains on the Fld surface have been individually modified, eitherby the introduction of positive charges or by their neutralization. Our results indicate that although Glu16,Glu20, Glu61, Asp65, and Asp96 contribute to the orientation and optimization of the Fld interaction,either with FNR or with photosystem I (PSI) (presumably through the formation of salt bridges), forefficient ET, none of these side chains is involved in the formation of crucial salt bridges for optimalinteraction with FNR. These data support the idea that the FNR-Fld interaction is less specific than theFNR-Fd interaction. However, analysis of the reactivity of these mutated Flds toward the membrane-anchored PSI complex indicated that all mutants, except Glu16Gln, lack the ability to form a stable complexwith PSI. Thr12, Thr56, Asn58, and Asn97 are present in the close environment of the isoalloxazine ringof FMN in Anabaena Fld. Their roles in the interaction with and ET to FNR and PSI have also beenstudied. Mutants at these Fld positions indicate that residues in the close environment of the isoalloxazinering modulate the ability of Fld to bind to and to exchange electrons with its physiological counterparts.