In organisms, various protective mechanisms against oxidative damaging of proteins exist. Here, we show that cofactor binding is among these mechanisms, because flavin mononucleotide (FMN) protects Azotobacter vinelandii flavodoxin against hydrogen peroxide-induced oxidation. We identify an oxidation sensitive cysteine residue in a functionally important loop close to the cofactor, i.e., Cys69....

Electron transfer reactions between Clostridum pasteurianum flavodoxin semiquinone and various oxidants [horse heart cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic acid (EDTA)] have been studied as a function of ionic strength by using stopped-flow spectrophotometry. The cytochrome c reaction is complicated by the existence of two cytochrome species which react at different r...

Flavodoxin II from Azotobacter vinelandii is a "long-chain" flavodoxin and has one of the lowest E1 midpoint potentials found within the flavodoxin family. To better understand the relationship between structural features and redox potentials, the oxidized form of the C69A mutant of this flavodoxin was crystallized and its three-dimensional structure determined to a resolution of 2.25 A by mole...

Interpretation of a new electron-density map at 3.25-A resolution has led to a somewhat revised model for the free radical (semiquinone) structure of flavodoxin from Clostridium MP. Although the general conformation of the molecule is very similar to that of oxidized Desulfovibrio vulgaris flavodoxin, flavin mononucleotide-protein interactions are not identical in the two flavodoxins. In the Cl...

As part of a series of comparisons of the structures of the three oxidation states of flavodoxin from Clostridium MP, phases for the semiquinonc form were determined to 2.0 A resolution by isomorphous replacement ( = 0.725). Subsequently, the structure was refined at 1.8 A resolution by a combination of difference Fourier, real space and reciprocal space methods. After refining to an R of 0...

Substitution of the noniron protein flavodoxin for the iron–sulfur protein ferredoxin is an iron-stress response employed by a variety of unicellular organisms, including many phytoplankton. The relative abundance of these two proteins has been shown to vary with the severity of growth limitation by iron in marine diatoms. During the IronEx II mesoscale iron-enrichment experiment, large volume ...

A recent study of experimental results for flavodoxin-like folds suggests that proteins from this family may exhibit a similar, signature pattern of folding intermediates. We study the folding landscapes of three proteins from the flavodoxin family (CheY, apoflavodoxin, and cutinase) using a simple nucleation and growth model that accurately describes both experimental and simulation results fo...

Flavodoxins synthesized by Azotobacter vinelandii strain UW 36 during growth on nitrate as nitrogen source were separated by FPLC on a Mono Q column into two species, flavodoxin 1 (AvFld 1) and flavodoxin 2 (AvFld 2). Both proteins migrated as single bands on SDS/PAGE. AvFld 1 was approx. 5-fold more abundant than AvFld 2 in the unresolved flavodoxin mixture. N-terminal amino acid analysis show...

Data regarding the role of oxygen in nitrite reduction are presented. In an NADPH-generating system including homogeneously purified ferredoxin-NADP reductase, ferredoxin (or flavodoxin) and nitrite reductase from the alga Bumilleriopsis filiformis, oxygen and nitrite can be reduced simultaneously. In air, rates of 1.2 mumol nitrite reduced-min-1-mg-1 nitrite reductase are obtained, which are p...