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Biomedical subjects

M Bruschi

Publications and source records attributed to M Bruschi.

At least 127 records · Page 7Linked to original sources
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

Phylogenetic studies of two rubredoxins from sulfate reducing bacteria.

The sequences of two rubredoxins isolated from the sulfate reducing bacteria: Desulfovibrio vulgaris and Desulfovibrio gigas have been elucidated. They have similar sequences but many more differences occur than would be expected from two bacteria of the same genus. Of the 52 sites, only 37 are occupied by identical residues. The primary structures are compared with those of the anaerobic bacteria rubredoxins of Clostridium pasteurianum, Micrococcus aerogenes, Pseudomonas oleovorans and Peptostreptococcus elsdenii: only 12 identities are found, mostly in the two clusters that contain two iron-bound cysteines each. A phylogenetic tree based on the primary structures is presented and possible relations with plant and bacterial ferredoxins are discussed. A secondary and tertiary structure stereochemically compatible with the sequence data, is proposed.

Amino Acid Sequence↗
PubMed1977

Cytochrome c-551.5 (c7) from Desulfuromonas acetoxidans.

Cytochrome c-551.5 of the anaerobic sulfur-reducing bacterium Desulfuromonas acetoxidans has been purified to homogeneity and characterized. It elicits absorption bands at 551.5, 522.5 and 418 nm in the reduced form; the absorptivity ratio Aalpha(red)/A280nm(ox) equals 3.8 for the pure preparation. The molecular weight was estimated to be 9800 by gel filtration. Determination of the amion acid composition and analysis of the N-terminal amino acid sequence showed the cytochrome to be identical with the threehaem cytochrome c-551.5 (c7) isolated from the syntrophic mixed culture Chloropseudomonas ethylica strain 2K. The occurrence of multihaem cytochromes c in bacteria is discussed.

Amino Acid Sequence↗
PubMed1977

Spectroscopic studies of the oxidation-reduction properties of three forms of ferredoxin from Desulphovibrio gigas.

Electron paramagnetic resonance spectra were recorded of three forms of Desulphovibrio gigas ferredoxin, FdI, FdI' and FdII. The g = 1.94 signal seen in dithionite-reduced samples is strong in FdI, weaker in FdI' and very small in FdII. The g = 2.02 signal in the oxidized proteins is weak in FdI and strongest in FdII. It is concluded that most of the 4Fe-4S centres in FdI change between states C- and C2-; FdI' contain both types of centre. There is no evidence that any particular centre can change reversibly between all three oxidation states. Circular dichroism spectra show differences between FdI and FdII even in the diamagnetic C2- state. The redox potentials of the iron-sulphur centres of the three oligomers (forms) are different. After formation of the apo-protein of FdII and reconstitution with iron and sulphide, the protein behaves more like FdI, showing a strong g = 1.94 signal in the reduced states.

Binding Sites↗
PubMed1977

NMR characterization of three forms of ferredoxin from Desulphovibrio gigas, a sulphate reducer.

A NMR and magnetic susceptibility study of the oxidized and reduced states of three different oligomers (forms) of a [4Fe-4S] ferrodoxin protein from Desulphovibrio gigas, FdI, FdI', and FdII was carried out. FdI and FdI' are different trimers and FdII a tetramer of the same basic subunit. A probable assignment of the contact shifted resonances is indicated. Since the temperature dependences of the contact shifted responances associated with each [4Fe-4S] are not all similar a delocalized model for the spin densities on the 4Fe does not apply. The exchange rate between oxidized and reduced states is slow on the NMR time scale. The three oligomers are not magnetically equivalent. Using the "three state hypothesis" terminology it is shown that FdIox is predominantly in the C2- state and changes upon reduction into the C3- state, while FdIIox is in the C- state and changes into the C2- state. FdI' does not easily fit into this classification. This study shows a similarity of magnetic behaviour between FdI and bacterial ferredoxins (e.g. Bacillus polymyxa) and between FdII and HiPIP from Chromatium sp. The influence of the quaternary structure on the stabilization of the different oxidation states of ferredoxins as well as on their redox potentials is discussed.

Desulfovibrio↗
PubMed1977

Purification and characterization of cytochrome c3, ferredoxin, and rubredoxin isolated from Desulfovibrio desulfuricans Norway.

Different electron carriers of the non-desulfoviridin-containing, sulfate-reducing bacterium Desulfovibrio desulfuricans (Norway strain) have been studied. Two nonheme iron proteins, ferredoxin and rubredoxin, have been purified. This ferredoxin contains four atoms of non-heme iron and acid-labile sulfur and six residues of cysteine per molecule. Its amino acid composition suggests that it is homologous with the other Desulfovibrio ferredoxins. The rubredoxin is also an acidic protein of 6,000 molecular weight and contains one atom of iron and four cysteine residues per molecule. The amino acid composition and molecular weight of the cytochrome c3 from D. desulfuricans (strain Norway 4) are reported. Its spectral properties are very similar to those of the other cytochromes c3 (molecular weight, 13,000) of Desulfovibrio and show that it contains four hemes per molecule. This cytochrome has a very low redox potential and acts as a carrier in the coupling of hydrogenase and thiosulfate reductase in extracts of Desulfovibrio gigas and Desulfovibrio desulfuricans (Norway strain) in contrast to D. gigas cytochrome c3 (molecular weight, 13,000). A comparison of the activities of the cytochrome c3 (molecular weight, 13,000) of D. gigas and that of D. desulfuricans in this reaction suggests that these homologous proteins can have different specificity in the electron transfer chain of these bacteria.

Amino Acids↗
PubMed1976

Purification, characterization and biological activity of three forms of ferredoxin from the sulfate-reducing bacterium Desulfovibrio gigas.

Three forms of ferredoxin FdI, FdI', and FdII have been isolated from Desulfovibrio gigas, a sulfate reducer. They are separated by a combination of DEAE-cellulose and gel filtration chromatographic procedures. FdI and FdI' present a slight difference in isoelectric point which enables the separation of the two forms over DEAE-cellulose, while FdII is easily separated from the two other forms by gel filtration. The three forms have the same amino acid composition and are isolated in different aggregation states. Molecular weight determinations by gel filtration gave values of 18 000 for FdI and FdI' and 24 000 for FdII, whereas a value of 6000 is determined when dissociation is accomplished with sodium dodecyl sulfate. The electronic spectra are different and their ultraviolet-visible absorbance rations are 0.77, 0.87 and 0.68 respectively for FdI, FdI' and FdII. Despite these differences, the physiological activities of the three forms are similar as far as the reduction of sulfite by molecular hydrogen is concerned.

Amino Acids↗
PubMed1976

[Perforating plantar ulcers in alcoholic polyneuritis. Physiopathology; clinical and instrumental findings].

Notes on the anatomical and physiological features of the circulation are followed by a description of the main physiopathological aspects of the terminal circulation of the lower extremities. Reference is made to the pathogenesis and clinical and instrumental diagnosis of plantar ulcers in alcoholic polyneuritis, along with the symtoms constantly observed in a series of some 30 cases.

Alcoholism↗