Crystal structure of the electron transfer complex rubredoxin–rubredoxin reductase of Pseudomonas aeruginosa

Abstract

Crude oil spills represent a major ecological threat because of the chemical inertness of the constituent n-alkanes. The Gramnegative bacterium Pseudomonas aeruginosa is one of the few bacterial species able to metabolize such compounds. Three chromosomal genes, rubB, rubA1, and rubA2 coding for an NAD(P)H:rubredoxin reductase (RdxR) and two rubredoxins (Rdxs) are indispensable for this ability. They constitute an electron transport (ET) pathway that shuttles reducing equivalents from carbon metabolism to the membrane-bound alkane hydroxylases AlkB1 and AlkB2. The RdxR-Rdx system also is crucial as part of the oxidative stress response in archaea or anaerobic bacteria. The redox couple has been analyzed in detail as a model system for ET processes. We have solved the structure of RdxR of P. aeruginosa both alone and in complex with Rdx, without the need for crosslinking, and both structures were refined at 2.40-and 2.45-Å resolution, respectively. RdxR consists of two cofactor-binding domains and a C-terminal domain essential for the specific recognition of Rdx. Only a small number of direct interactions govern mutual recognition of RdxR and Rdx, corroborating the transient nature of the complex. The shortest distance between the redox centers is observed to be 6.2 Å.

Structure of Human J-type Co-chaperone HscB Reveals a Tetracysteine Metal-binding Domain

“…These include solution structures of RanBP2/NZF type zinc finger domains found in nuclear pore complex protein Nup153 (Protein Data Bank codes 2ebr a The values in parentheses are for the highest resolution shell. The metal coordinating loops of all these proteins show local similarity to the "knuckles" of rubredoxin, a well known tetracysteine iron-binding protein involved in a range of redox reactions, including oxidative stress response pathways in microaerophillic/anaerobic bacteria (65). The structural alignment in Fig.…”

“…Structural Details of the N-domain-The core of the N-domain of HscB, which is relatively polar, is likely stabilized by hydrogen bonds between the side chain N-atom of Trp 48 , the side chain amide of Gln 65 , and the backbone carbonyl of Ala 63 ( Fig. 2a, inset 42 and Gln 65 are highly conserved in homologs of hHscB and are a crucial part of the consensus motif of the N-domain, CWXCX 9 -13 FCXXCXXXQ, identified from the multiple sequence alignment of these sequences (Fig.…”

The Maturation Factors HoxR and HoxT Contribute to Oxygen Tolerance of Membrane-Bound [NiFe] Hydrogenase in Ralstonia eutropha H16

“…The redox-active site consists of a central iron coordinated by four cysteines in a tetrahedral arrangement and switches between oxidation states of ϩ2 and ϩ3 at a midpoint potential around 0 mV (16). The exact role of most rubredoxins remains elusive, but some of them were shown to be involved in electron transfer reactions (27,53,66) and oxidative stress response in anaerobes (23,55,77). In contrast to common rubredoxins that contain two CXXCG sites, we identified a conserved CXXCW and CXXCD/E motif in the HoxR-related proteins (see Fig.…”

Quantitative PCR analysis of diesel degrading genes of Acinetobacter calcoaceticus isolates

“…Interestingly, novel genes encoding AlkB-Rubredoxin fusion proteins were used in the hydroxylation of long-chain alkanes by Gram positive bacteria (Nie et al, 2011). In addition, rubredoxin-rubredoxin reductase systems are present in many other organisms that are unable to degrade alkanes, where they serve other functions such as rapid transport of reducing equivalents to the final receptor (Hagelueken et al, 2007). Although, rubA, rubB and estB constitute an operon in Acinetobacter sp.…”