Showing papers by "Isabel Moura published in 2005"
TL;DR: A nitrate reductase was solubilized with Triton X-100 from the membranes of Pseudomonas chlororaphis DSM 50135 grown microaerobically in the presence of nitrate, and electrocatalytic studies revealed that only the membrane-bound, not the solubILized form of the enzyme, can accept electrons from a menaquinone analog, menadione, whereas both forms canaccept electrons from methylviologen.
10 citations
TL;DR: In this paper, the oxidized form of Treponema pallidum superoxide reductase was crystallized in the presence of polyethylene glycol and magnesium chloride and two crystal forms were obtained depending on the oxidizing agents used after purification.
Abstract: Superoxide reductase is a 14 kDa metalloprotein containing a catalytic non-haem iron centre [Fe(His)4Cys]. It is involved in defence mechanisms against oxygen toxicity, scavenging superoxide radicals from the cell. The oxidized form of Treponema pallidum superoxide reductase was crystallized in the presence of polyethylene glycol and magnesium chloride. Two crystal forms were obtained depending on the oxidizing agents used after purification: crystals grown in the presence of K3Fe(CN)6 belonged to space group P21 (unit-cell parameters a = 60.3, b = 59.9, c = 64.8 A, β = 106.9°) and diffracted beyond 1.60 A resolution, while crystals grown in the presence of Na2IrCl6 belonged to space group C2 (a = 119.4, b = 60.1, c = 65.6 A, β = 104.9°) and diffracted beyond 1.55 A. A highly redundant X-ray diffraction data set from the C2 crystal form collected on a copper rotating-anode generator (λ = 1.542 A) clearly defined the positions of the four Fe atoms present in the asymmetric unit by SAD methods. A MAD experiment at the iron absorption edge confirmed the positions of the previously determined iron sites and provided better phases for model building and refinement. Molecular replacement using the P21 data set was successful using a preliminary trace as a search model. A similar arrangement of the four protein molecules could be observed.
3 citations
TL;DR: Two proteins were purified and preliminarily characterized from the soluble extract of cells of the aminolytic and peptidolytic sulfate-reducing bacterium Desulfovibrio (D.) aminophilus and presents similarities with the tetraheme cytochrome c3 from Desulfomicrobium (Des.) norvegicum.
Abstract: Two proteins were purified and preliminarily characterized from the soluble extract of cells (310 g, wet weight) of the aminolytic and peptidolytic sulfate-reducing bacterium Desulfovibrio (D.) aminophilus DSM 12254. The iron-sulfur flavoenzyme adenylylsulfate (adenosine 5'-phosphosulfate, APS) reductase, a key enzyme in the microbial dissimilatory sulfate reduction, has been purified in three chromatographic steps (DEAE-Biogel A, Source 15, and Superdex 200 columns). It contains two different subunits with molecular masses of 75 and 18 kDa. The fraction after the last purification step had a purity index (A278nm / A388nm) of 5.34, which was used for further EPR spectroscopic studies. The D. aminophilus APS reductase is very similar to the homologous enzymes isolated from D. gigas and D. desulfuricans ATCC 27774. A tetraheme cytochrome c3 (His-heme iron-His) has been purified in three chromatographic steps (DEAE- Biogel A, Source 15, and Biogel-HTP columns) and preliminarily characterized. It has a purity index ([A553nm - A570nm]red / A280nm) of 2.9 and a molecular mass of around 15 kDa, and its spectroscopic characterization (NMR and EPR) has been carried out. This hemoprotein presents similarities with the tetraheme cytochrome c3 from Desulfomicrobium (Des.) norvegicum (NMR spectra, and N-terminal amino acid sequence).
3 citations