Role of Hydrophobic Interactions in the Flavodoxin Mediated Electron Transfer from Photosystem I to Ferredoxin-NADP+ Reductase in Anabaena PCC 7119
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- 作者：Isabel Nogué ; s ; Marta Martí ; nez-Jú ; lvez ; José ; A. Navarro ; Manuel Hervá ; s ; Lorena Armenteros ; Miguel Angel de la Rosa ; Tammy B. Brodie ; John K. Hurley ; Gordon Tollin ; Car
- 刊名：Biochemistry
- 出版年：2003
- 出版时间：February 25, 2003
- 年：2003
- 卷：42
- 期：7
- 页码：2036 - 2045
- 全文大小：151K
- 年卷期：v.42,no.7(February 25, 2003)
- ISSN：1520-4995
文摘
Hydrophobic interactions play an active role in effective complex formation between ferredoxin-NADP+ reductase (FNR) and ferredoxin (Fd) from Anabaena, where an aromatic amino acid residue onthe Fd surface (F65) and three hydrophobic residues (L76, L78, and V136) on the reductase surface havebeen shown to be essential for the efficient electron transfer (ET) reaction between Fd and FNR (Martínez-Júlvez et al. (2001) J. Biol. Chem. 276, 27498-27510). Since in this system flavodoxin (Fld) can efficientlyreplace Fd in the overall ET process, we have further investigated if such hydrophobic interactions arealso critical in complex stabilization and ET in the FNR/Fld association. Different ET behaviors with Fldare observed for some of the mutations made at L76, L78, and V136 of Anabaena FNR. Thus, the ETinteraction with Fld is almost completely lost upon introduction of negatively charged side chains atthese positions, while more conservative changes in the hydrophobic patch can influence the rates of ETto and from Fld by altering the binding constants and the midpoint redox potentials of the flavin group.Therefore, our results confirm that nonpolar residues in the region close to the FAD group in FNR participatein the establishment of interactions with Fld, which serve to orient the two flavin groups in a mannersuch that ET is favored. In an attempt to look for the counterpart region of the Fld surface, the effectproduced by the replacement of the only two nonpolar residues on the Fld surface, I59 and I92, by a Lyshas also been analyzed. The results obtained suggest that these two hydrophobic residues are not criticalin the interaction and ET processes with FNR. The reactivity of these I92 and I59 Fld mutants toward themembrane-anchored photosystem I (PSI) complex was also analyzed by laser flash absorption spectroscopy.From these data, significant effects are evident, especially for the I92 position of Fld, both in the associationconstant for complex formation and in the electron-transfer rate constant in the PSI/Fld system.