Search

Structural and charge interaction analyses of the binding site of the aspartate 95 mutants of the Desulfovibrio vulgaris flavodoxin reveals the role played by the hydrogen bonding in the modulation of the redox potentials of the bound flavodoxin, particularly the carboxylate group of the mutant.

Scalar couplings were detected across NH...OP and OH...OP hydrogen bonds in a flavoprotein.

Purification of a dehydratase to homogeneity from a cell-free extract of Bacillus sp. strain OxB-1 is analyzed. Results demonstrate that the gene coding for the enzymes has been cloned into the plasmid.

Research was conducted to examine the ability of glycine-61 in controlling flavin redox potentials and in stabilizing the semiquinone of FMN using mutants of the electron-transfer protein flavodoxin derived from 'Desulfovibrio vulgaris.' Wild-type and mutant flavodoxins were compared using their spectroscopic properties. Results indicate the destabilization of the semiquinone due to the lengthening of the side chain at position 61.

Flavodoxins are electron transfer proteins carrying a noncovalently bound mononucleotide molecule as the redox-active center. In many flavodoxins, the flavin is contained between two aromatic residues Trp57 and Tyr95. Each of the residues were replaced by alanine and leucine, and redox potentials and binding energies of the oxidized FMN-apoflavodoxin complexes were determined. Interaction between Tyr94 and FMN is thought to stabilize the apoflavodoxin-FMN complex in all redox states.

13C enriched cyanide was used to cyanylate both the thiol groups of Megasphaera elsdenii flavodoxin. An increase in the dissociation constant of the apoflavodoxin-flavin mononucleotide complex was noted. It was concluded that thiocyanate carbons will have a minimal chemical shift of 109 ppm in apolar solvents which do not contain hydrogen bond donors and that the chemical shift of a thiocyanate carbon can be used as a probe of its molecular environment. A discussion has arisen on the role of chemical shifts of the thiocyanate carbon of cyanylated apoflavodoxin, flavodoxin and other proteins and how it depends on the microenvironments of the thiocyanate group.

The study shows that photosynthetic bacterium Rhodobacter capsulatus contains a ferredoxin (flavodoxin)-NADP(H) oxidoreductase (FPR) that catalyzes electron transfer between NADP(H) and ferredoxin or flavodoxin. The result shows that one-electron reduction of oxidized flavodoxin limits the enzyme activity in vitro, supports the notion that flavodoxin oscillates between the semiquinone and fully reduced states when FPR operates in vivo.

The contribution of three neighboring flavin mononucleotide molecule (FMN) residues, Thr56, Asn58, and Asn97, and of three negatively charged surface residues Glu20, Asp65, and Asp96, to modulate the redox properties of FMN upon its binding to the apoprotein is investigated. Also, the role of these residues in the apoflavodoxin: FMN interaction is analyzed.

A study was conducted to investigate the interactions and electron-transfer properties of ferrodoxin-NADP(super +) reductase (FNR) proteins mutated at their C-termini. The result indicates that interactions with Fd or Fld are hardly affected by replacement of this tyrosine by tryptophan, phenylalanine, or serine.

A study was conducted to analyze pH-dependent spectroscopic changes related to the hydroquinone of FMN in flavodoxins. Flavodoxin from D. vulgaris was determined as the recombinant protein. Results indicated that a decrease in pH promotes a change in the electronic structure of the reduced flavin resulting from changes in the ionization state of the flavin and in the hydrogen-bonding network around the flavin.