Journal of Biochemistry Advance Access published online on January 3, 2009
Journal of Biochemistry, doi:10.1093/jb/mvn185
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In vitro and in vivo interactions of Ferredoxin-NADP+ reductases in Pseudomonas putida
1 Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 136-075, Korea; 2Department of Life Science, Chung-Ang University, Seoul, 156-756, Korea; 3Department of Microbiology, Cornell University, Ithaca, NY 14853-8101, USA; 4Environmental Biotechnology National Core Research Center, Gyeongsang National University, Jinju 660-701, Korea
*To whom correspondence should be addressed: Woojun Park, Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 136-075. Tel: +82-2-3290-3067; Fax: +82-2-953-0737; E-mail: wpark{at}korea.ac.kr
Received November 26, 2008; Accepted December 26, 2008
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Ferredoxin-NADP+reductase (Fpr) is known to control NADP+/NADPH pool in proteobacteria. There is only one fpr gene present in most proteobacteria, but Pseudomonas putida has two Fprs (FprA, FprB). We elucidated the functional relationships between the two types of Fpr and their electron transport partners [ferredoxin (Fd) and flavodoxin (Fld)] by cloning, expressing, and preparing these proteins in various combinations and assessing their properties in vitro and in vivo using biochemical assays, the Far-western analysis, the yeast two-hybrid assay, and structural molecular modeling. Both of the Fprs have a lower Km value for NADPH than for NADH in the diaphorase assays. With NADH as electron donor, FprB also has a high specific constant (kcat/Km) in the diaphorase assay. The catalytic efficiency of FprA is higher when Fld is present as its redox partner, compared to the kinetics observed with other electron transport partners in a NADPH-dependent cytochrome c reduction assay. The highest specific constant (kcat/Km) of FprB was observed in the presence of FdA. FprB's Km value and catalytic activity (kcat) with NADH were significant in cytochrome c reduction assays. Strong kinetic interactions of Fprs with their redox partners were also demonstrated by homology modeling, the Far-western analysis and the in vivo yeast two-hybrid system. This study demonstrates for the first time that Fprs in P. putida function as diaphorase, ferredoxin/flavodoxin reductases and determines their preferred redox partner in vivo and in vitro.
Key Words: Oxidative stress, Homology modeling, Far-Western Blot, Protein-protein interaction, Pseudomonas putida KT2440