PubMed Health⌕ Search

Biomedical subjects

J LeGall

Publications and source records attributed to J LeGall.

158 records · Page 9Linked to original sources
PubMed1980

Evidence for a three-iron center in a ferredoxin from Desulfovibrio gigas. Mössbauer and EPR studies.

The tetrameric form of a Desulfovibrio gigas ferredoxin, named Fd II, mediates electron transfer between cytochrome c3 and sulfite reductase. We have studied two stable oxidation states of this protein with Mössbauer spectroscopy and electron paramagnetic resonance. We found 3 iron atoms/monomer and a spin concentration of 0.9 spins/monomer for the oxidized protein. Taken together, the EPR and Mössbauer data demonstrate conclusively the presence of a spin-coupled structure containing 3 iron atoms and labile sulfur. The Mössbauer data show also that this metal center is structurally similar, if not identical, with the low potential center of a ferredoxin from Azotobacter vinelandii, a novel cluster described recently (Emptage, M.H., Kent, T.A., Huynh, B.H., Rawlings, J., Orme-Johnson, W.H., and Münck, E. (1980) J. Biol. Chem. 255, 1793-1796).

Desulfovibrio↗
PubMed1978

Structural homology of cytochromes c.

Cytochromes c from many eukaryotic and diverse prokaryotic organisms have been investigated and compared using high-resolution nuclear magnetic resonance spectroscopy. Resonances have been assigned to a large number of specific groups, mostly in the immediate environment of the heme. This information, together with sequence data, has allowed a comparison of the heme environment and protein conformation for these cytochromes. All mitochondrial cytochromes c are found to be very similar to the cytochromes c2 from Rhodospirillaceae. In the smaller bacterial cytochromes, Pseudomonas aeruginosa cytochrome c551 and Euglena gracilis cytochrome c552, the orientation of groups near the heme is very similar, but the folding of the polypeptide chain is different. The heme environment of these two proteins is similar to that of the larger bacterial and mitochondrial cytochromes. Two low-potential cytochromes, Desulfovibrio vulgaris cytochrome c553 and cytochrome c554 from a halotolerant micrococcus have heme environments which are not very similar to those of the other proteins reported here.

Amino Acids↗
PubMed1977

A four-iron, four-sulfide ferredoxin with high thermostability from Clostridium thermoaceticum.

A ferredoxin containing only one [Fe4S4] cluster was purified from Clostridium thermoaceticum. It has a molecular weight of about 7,300, a partial specific volume of 0.67, and an isoelectric point of 3.25. Its absorption spectrum has two maxima at 390 nm (epsilon = 16.8 X 10(3)M-1cm-1) and at 280 nm (epsilon = 24.2 X 10(3)M-1cm-1). The absorption at 390 nm is almost half that of other clostridial ferredoxins, which have two [Fe4S4] clusters, and is similar to other ferredoxins with only one [Fe4S4] cluster. The ferredoxin had high thermal stability and retained over 50% of its activity after treatment at 80 degrees C. It functions in the transfer of electrons from pyruvate to nicotinamide adenine dinucleotide phosphate (NADP), which indicates the presence of pyruvate:ferredoxin oxidoreductase and reduced ferredoxin-NADP reductase in C, thermoaceticum. NADPH is used in the synthesis of acetate from CO2 in this organism.

Amino Acids↗
PubMed1973

Isolation of assimilatroy- and dissimilatory-type sulfite reductases from Desulfovibrio vulgaris.

Bisulfite reductase (desulfoviridin) and an assimilatory sulfite reductase have been purified from extracts of Desulfovibrio vulgaris. The bisulfite reductase has absorption maxima at 628, 580, 408, 390, and 279 nm, and a molecular weight of 226,000 by sedimentation equilibrium, and was judged to be free of other proteins by disk electrophoresis and ultracentrifugation. On gels, purified bisulfite reductase exhibited two green bands which coincided with activity and protein. The enzyme appears to be a tetramer but was shown to have two different types of subunits having molecular weights of 42,000 and 50,000. The chromophore did not form an alkaline ferrohemochromogen, was not reduced with dithionite or borohydride, and did not form a spectrally visible complex with CO. The assimilatory sulfite reductase has absorption maxima at 590, 545, 405 and 275 nm and a molecular weight of 26,800, and appears to consist of a single polypeptide chain as it is not dissociated into subunits by sodium dodecyl sulfate. By disk electrophoresis, purified sulfite reductase exhibited a single greenish-brown band which coincided with activity and protein. The sole product of the reduction was sulfide, and the chromophore was reduced by borohydride in the presence of sulfite. Carbon monoxide reacted with the reduced chromophore but it did not form a typical pyridine ferrohemochromogen. Thiosulfate, trithionate, and tetrathionate were not reduced by either enzyme preparation. In the presence of 8 M urea, the spectrum of bisulfite reductase resembles that of the sulfite reductase, thus suggesting a chemical relationship between the two chromophores.

Bacterial Proteins↗