The consecutive structural genes for the iron-sulfur flavoenzyme sulfide dehydrogenase, sudB and sudA, have been identified in the genome of Pyrococcus furiosus. The translated sequences encode a heterodimeric protein with an alpha-subunit, SudA, of 52598 Da and a beta-subunit, SudB, of 30686 Da. The alpha-subunit carries a FAD, a putative nucleotide binding site for NADPH, and a [2Fe-2S]2+,+ prosthetic group. The latter exhibit EPR g-values, 2.035, 1.908, 1.786, and reduction potential, Em,8 = +80 mV, reminiscent of Rieske-type clusters; however, comparative sequence analysis indicates that this cluster is coordinated by a novel motif of one Asp and three Cys ligands. The motif is not only found in the genome of hyperthermophilic archaea and hyperthermophilic bacteria, but also in that of mesophilic Treponema pallidum. The beta-subunit of sulfide dehydrogenase contains another FAD, another putative binding site for NADPH, a [3Fe-4S]+,0 cluster, and a [4Fe-4S]2+,+ cluster. The 3Fe cluster has an unusually high reduction potential, Em,8 = +230 mV. The reduced 4Fe cluster exhibits a complex EPR signal, presumably resulting from magnetic interaction of its S = 1/2 spin with the S=2 spin of the reduced 3Fe cluster. The 4Fe cluster can be reduced with deazaflavin/EDTA/light but not with sodium dithionite; however, it is readily reduced with NADPH. SudA is highly homologous to KOD1-GO-GAT (or KOD1-GltA), a single-gene encoded protein in Pyrococcus kodakaraensis, which has been putatively identified as hyperthermophilic glutamate synthase. However, P. furiosus sulfide dehydrogenase does not have glutamate synthase activity. SudB is highly homologous to HydG, the gamma-subunit of P. furiosus NiFe hydrogenase. The latter enzyme also has sulfide dehydrogenase activity. The P. furiosus genome contains a second set of consecutive genes, sudY and sudX, with very high homology to the sudB and sudA genes, and possibly encoding a sulfide dehydrogenase isoenzyme. Each subunit of sulfide dehydrogenase is a primary structural paradigm for a different class of iron-sulfur flavoproteins.

Gene and protein expression displays circadian oscillations in numerous body organs. These oscillations can be disrupted in diseases, thus contributing to the disease pathology. Whether the molecular architecture of cortical brain regions oscillates daily and whether these oscillations are modified in brain disorders is less understood. We identified 1200 daily oscillating transcripts in the hippocampus of control mice. More transcripts (1600) were oscillating in experimental epilepsy, with only one fourth oscillating in both conditions. Proteomics confirmed these results. Metabolic activity and targets of antiepileptic drugs displayed different circadian regulation in control and epilepsy. Hence, the hippocampus, and perhaps other cortical regions, shows a daily remapping of its molecular landscape, which would enable different functioning modes during the night/day cycle. The impact of this remapping in brain pathologies needs to be taken into account not only to study their mechanisms, but also to design drug treatments and time their delivery.

The acute-phase response alters the composition of carrier proteins in plasma, which may affect the blood deposition and transport of biomediators and drugs. The effect of the acute-phase response on the ligand binding ability of plasma was studied in leukemic children with and without systemic inflammation (sepsis and septic shock). To target different transport proteins, differentially charged fluorescent dyes were used: anionic ANS (8-anilinonaphthalene-1-sulfonate), uncharged Nile red, and cationic Quinaldine red. Human serum albumin was a principal carrier for ANS and competed for Nile red binding with lipoproteins. The synchro-scan fluorescence spectra of Nile red in plasma distinguished two species of the dye bound to serum albumin and to low-density and/or very low-density lipoproteins. The binding of Quinaldine red did not correlate with albumin and lipoprotein levels, and was probably determined by alpha(1)-acid glycoprotein. Compared with the control group, leukemia increased Quinaldine red binding by 65% and did not significantly affect the binding of other probes. Sepsis and septic shock did not change the binding of Quinaldine red, but progressively decreased ANS binding, finally by about 33%, and shifted Nile red distribution from serum albumin toward lipoproteins. These changes reflected a modified composition of the three principal transport proteins in plasma in the acute-phase response. Simple and rapid fluorescent tests developed in this study can be used to evaluate the acute-phase response and to optimize drug administration protocols in clinical practice.