Disease relevance of fldA

• The fldA gene maps at 15.9 min on the E. coli chromosome and is transcribed in a counterclockwise direction [1].
• Lys75 of Anabaena ferredoxin-NADP+ reductase is a critical residue for binding ferredoxin and flavodoxin during electron transfer [2].
• The orthorhombic form (space group P2(1)2(1)2(1), a = 126.4, b = 41.10, c = 69.15 A, with two molecules per asymmetric unit) was solved initially by molecular replacement at a resolution of 3.0 A, using coordinates from the structure of the flavodoxin from Synechococcus PCC 7942 (Anacystis nidulans) [3].
• The deduced amino acid sequence, determined by nucleotide sequencing of the flavodoxin gene, shows strong homology with flavodoxins from nitrogen-fixing bacteria and cyanobacteria [1].
• The sequence Tyr 58-Tyr 59, in a bend near the FMN, has so far been found only in the flavodoxins from E. coli and Haemophilus influenzae, and may be important in interactions of flavodoxin with its partners in activation reactions [3].

High impact information on fldA

• IspH protein could also be activated by a mixture of flavodoxin, flavodoxin reductase, and NADPH at a rate of 3 nmol x min(-1) x mg(-1) [4].
• The FMN-binding domain is similar to the structure of flavodoxin, whereas the two C-terminal dinucleotide-binding domains are similar to those of ferredoxin-NADP+ reductase (FNR) [5].
• The nifJ gene of Klebsiella pneumoniae encodes an oxidoreductase required for the transfer of electrons from pyruvate to flavodoxin, which reduces nitrogenase [6].
• The structure revealed that each monomer of AzoR has a flavodoxin-like structure, without the explicit overall amino acid sequence homology [7].
• Fd-epsilon(88-stop) caused higher rates of uncoupled ATP hydrolysis than Fd-epsilon, and epsilon(88-stop) showed an increased rate of membrane-bound ATP hydrolysis but decreased proton pumping relative to the wild type [8].

Chemical compound and disease context of fldA

• We therefore conclude that dA1 is identical with E. coli ferredoxin (flavodoxin) NADP+ reductase [9].
• We propose that the amino acid sequence similarity between E. coli flavodoxin-flavodoxin reductase and the putative FMN, FAD, and NAD(P)H binding regions of cytochrome P450 reductase provides the basis for the reconstitution of P450c17 activities by this bacterial system [10].
• Methionine synthase from E. coli catalyzes its own reactivation by a reductive methylation that involves electron transfer from reduced flavodoxin and methyl transfer from AdoMet [11].
• Mutagenesis of two acidic Anabaena Fld residues (D144A and E145A) significantly decreased flavodoxin-supported P450c17 progesterone 17alpha-hydroxylase activity [12].
• Postulating the native E. coli flavodoxin/flavodoxin reductase system might mimic the natural redox partners of P450(cin), it was expressed in E. coli in the presence of cineole 1 [13].

Biological context of fldA

• The deduced amino acid sequence shows a high extent of sequence identity with that of various ferredoxin (flavodoxin) NADP+ reductases [9].
• Mutation of aspartate 757 to glutamate results in a cob(II)alamin enzyme that is approximately 70% four-coordinate, and reductive methylation of this enzyme using flavodoxin hydroquinone as the electron donor proceeds through a kinetically competent cob(I)alamin intermediate [11].
• A flavodoxin that is required for enzyme activation: the structure of oxidized flavodoxin from Escherichia coli at 1.8 A resolution [3].
• All of these mutants have been assayed for reactivity with Fd and Fld using steady-state and stopped-flow kinetics [14].
• Because the phenotype of a flavodoxin mutant is not known, we used this degenerate probe to screen the phages of the Kohara library and identified two phages, with inserts mapping at approximately 16 min, that hybridized to the probe [1].

Associations of fldA with chemical compounds

• NADPH, ferredoxin, flavodoxin, or ferredoxin (flavodoxin):NADP+ reductase could not reduce SoxR directly in vitro at a measurable rate [15].
• Flavodoxin reductase, possessing FAD as a cofactor, is able to reconstitute P450c17 activities only in the presence of flavodoxin, an FMN-containing protein, and NAD(P)H [10].
• In this paper, we show that even in the presence of the strong reductant flavodoxin hydroquinone, cob(I)alamin is not observed as a significant intermediate [11].
• Together, they catalyze the reduction of ribonucleoside triphosphates to the corresponding deoxyribonucleotides in the presence of S-adenosylmethionine, reduced flavodoxin or reduced deazaflavin, potassium ions, dithiothreitol, and formate [16].
• Its function is to mediate electron transfer from reduced flavodoxin to S-adenosylmethionine, required for the introduction of a glycyl radical in the large component, named protein alpha, which then becomes active for the reduction of ribonucleotides [17].

Physical interactions of fldA

• The enzyme ferredoxin-NADP(+) reductase (FNR) forms a 1 : 1 complex with ferredoxin (Fd) or flavodoxin (Fld) that is stabilised by both electrostatic and hydrophobic interactions [14].

Other interactions of fldA

• In Escherichia coli, flavodoxin is the physiological electron donor for the reductive activation of the enzymes pyruvate formate-lyase, anaerobic ribonucleotide reductase, and B12-dependent methionine synthase [3].

Analytical, diagnostic and therapeutic context of fldA

• E. coli flavodoxin binds P450c17 directly and with relatively high affinity (apparent Ks approximately 0.2 microM) at low ionic strength, as evidenced by a change in spin state of the P450c17 heme iron upon titration with flavodoxin [10].
• The overall fold of SiR-FP18 is very similar to that of bacterial flavodoxins and of the flavodoxin-like domain in CPR or P450-BM3 [18].
• To characterize the binding interface between E. coli flavodoxin and methionine synthase, we have employed site-directed mutagenesis and chemical cross-linking using carbodiimide and N-hydroxysuccinimide [19].
• However, degradation of a mutant flavodoxin carrying a substitution of Tyr94 to Asp with a lower affinity for FMN could be monitored by fluorimetry [20].
• With a mixture of flavodoxin, flavodoxin reductase, and NADPH as the reducing agent, stringent assay methods based on photometry or on 13C NMR detection of multiply 13C-labeled substrate/product ratios afforded catalytic activities greater than 60 nmol mg(-1) min(-1) for the protein "as isolated" (i.e., without reconstitution of any kind) [21].

References