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Biomedical subjects

D Barra

Publications and source records attributed to D Barra.

At least 145 records · Page 8Linked to original sources
PubMed1983

Sequence homology between prokaryotic and eukaryotic forms of serine hydroxymethyltransferase.

The sequence of tryptic and chymotryptic peptides from cytosolic and mitochondrial rabbit liver serine hydroxymethyltransferase are compared to the proposed sequence of a protein coded for by the glyA gene of Escherichia coli. The E. coli glyA gene is believed to code for serine hydroxymethyltransferase. Extensive sequence homology between these peptides were found for the proposed E. coli enzyme in the aminoterminal two-thirds of the molecule. All three proteins have identical sequences from residue 222-231. This sequence is known to contain the lysyl residue which forms a Schiff's base with pyridoxal-P in the two rabbit liver enzymes. These results support the interpretation that the proposed sequence of E. coli serine hydroxymethyltransferase is correct. The data also show that cytosolic and mitochondrial serine hydroxymethyltransferase are homologous proteins.

Amino Acid Sequence↗
PubMed1983

Heterogeneity of the basic pancreatic inhibitor (Kunitz) in various bovine organs.

Four protein protease inhibitors (I, II, III, IV) having low molecular weights (10 600-6500) and basic isoelectric points were isolated by affinity chromatography from bovine spleen. Inhibitor IV was identified as the basic pancreatic trypsin inhibitor (Kunitz inhibitor); the presence and distribution of components I, II and III vary in the different bovine organs. Spleen inhibitors I, II, III and IV were purified by ion-exchange chromatography; they form 1:1 complexes with trypsin and inhibit enzymatic activity of trypsin, chymotrypsin and kallikrein. Inhibitors I, II and III contain carbohydrate moieties (7-4%) covalently bound to the polypeptide chain. Specific basic pancreatic trypsin inhibitor antiserum has shown the complete identity between inhibitor IV and the basic pancreatic trypsin inhibitor, while partial cross-reactivity between the basic pancreatic trypsin inhibitor and inhibitors I, II and III can be seen from a double immunodiffusion test.

Animals↗
PubMed1983

Primary structure of hemoglobin from trout (Salmo irideus) amino acid sequence of the beta chain of trout Hb I.

The amino acid sequence of the beta chain of trout Hb I is presented; it adds to the previously reported sequence of the alpha chain (Bossa et al. (1978) Biochim. Biophys. Acta 536, 298-305), thus completing the primary structure of the hemoglobin component of trout's blood devoid of heterotropic phenomena. Comparison of beta chain from trout Hb I with the corresponding sequences from human and carp shows differences of 46.6% and 34.7%, respectively; the sequence (almost completed) of the beta chain from the other major hemoglobin component of trout, i.e., trout Hb IV, displays more differences (41.6%) from beta trout Hb I than from the corresponding chain of other fishes, such as carp or goldfish.

Amino Acid Sequence↗
PubMed1983

DNA-binding peptides from rat liver and Novikoff hepatoma cells: quantitative level and possible biochemical differences.

DNA isolated from rat liver by intensive deproteinization with chloroform/isoamyl alcohol and phenol contains low molecular weight peptides in a quantity of about 20 micrograms/mg DNA. These peptides show high specific activity in inhibiting transcription in a reconstituted cell-free system with prokaryotic and eukaryotic RNA polymerase. Their level is markedly decreased in DNA prepared from Novikoff hepatoma cells. Moreover the amino acid analysis and the pattern of analytical separation by high performance liquid chromatography (HPLC) show some biochemical differences between DNA-binding peptides extracted from rat liver and Novikoff hepatoma cells. The possibility that carcinogenesis may involve mechanisms which lead to selective removal of some components of the DNA-binding peptides, is discussed.

Amino Acids↗
PubMed1983

Primary structure of aspartate aminotransferase from horse heart and comparison with that of other homotopic and heterotopic isoenzymes.

Sulphydryl groups of mitochondrial aspartate aminotransferase from horse heart were titrated with 5,5'-dithiobis (2-nitrobenzoic acid). From analysis of peptic peptides, 378 amino acid residues (94.3% of the total) in the protein were identified. The results of amino acid sequence analysis are compared with those of cytosolic and mitochondrial aspartate aminotransferases from other sources.

Amino Acid Sequence↗
PubMed1983

Intestinal absorption of S-adenosyl-L-methionine in humans.

S-adenosyl-L-methionine (SAM) has proven to be fairly stable in gastric and duodenal juices as well as in bile. It was, therefore, administered orally to six healthy subjects. No increase in SAM levels was observed in the systemic blood. SAM was then directly injected into a jejunal loop of nine patients undergoing cholecystectomy. SAM concentrations increased significantly in venous mesenteric and systemic blood. Infusions of methionine directly into the jejunum by the same method used for SAM did not induce any increase in SAM concentrations in the mesenteric or systemic blood.

Female↗
PubMed1982

Carbamoylation of Cu,Zn-superoxide dismutase by cyanate. Role of lysines in the enzyme action.

Reaction with cyanate leads to a reversible change of the EPR spectrum of Cu,Zn-superoxide dismutase and to time-dependent carbamoylation of the lysine residues of the enzyme, producing a stable covalent derivative with more negative charge. The carbamoylated enzyme is less active than the native enzyme in spite of unaltered EPR spectra. The extent of this inactivation is much less when the enzyme activity is measured at low ionic strength. These results show that integrity of the active site is not the sole factor playing a role in the enzyme mechanism and that the ionic strength effect is related to electrostatic interactions between O-2 and surface charges of the protein.

Animals↗
PubMed1982

Synthesis of either Fe- or Mn-superoxide dismutase with an apparently identical protein moiety by an anaerobic bacterium dependent on the metal supplied.

Superoxide dismutase of Propionibacterium shermanii, an anaerobic that produces an iron superoxide dismutase, was purified from cells grown in iron-free conditions. The enzyme isolated was found to contain manganese and to have spectral and catalytic properties very similar to those of typical Mn-superoxide dismutases. Its electrophoretic mobility, molecular weight, and subunit size were identical with those of the Fe-enzyme. Amino acid compositions were practically indistinguishable in either case. The NH2-terminal sequence was found to be identical. The catalytic activity of an apoprotein sample prepared from the purified holoenzyme was restored by adding either Mn(II) or Fe(II). Only the metal/protein ratio varied from approximately 1 per subunit in the case of the Fe-enzyme to approximately 2 for the Mn-enzyme. It is concluded that this bacterium can accommodate either Fe or Mn on identical, or very slightly dissimilar, proteins forming active sites with the properties found in specific metallodismutases.

Amino Acids↗
PubMed1982

Small peptides controlling transcription in vitro are bound to chromatin DNA.

Low-molecular-weight peptides are linked to the chromatin DNA of several tissues, from which they can be dissociated by alkaline extraction at pH 9.5. The level of the active peptide fraction ranges between 10 and 35 micrograms/mg DNA. The removal of peptides from DNA causes a relevant amplification of DNA template capacity for prokaryotic and eukaryotic RNA polymerases. Gel filtration on Sephadex G-25 or BioGel P4 shows that the chromatin peptide fraction from purified DNA migrates as a sharp peak with an elution volume corresponding to a molecular weight of about 1000. The chromatin peptides are further purified by Sephadex G-10 and high-performance liquid chromatography. Four active fractions are isolated, one of which shows very high inhibition activity on the RNA synthesis in vitro. The amino acid analysis and the inhibition mechanism of the purified peptides are reported.

Animals↗
PubMed1982

Structural comparison of the haemoglobin components of the armoured catfish Pterygoplichthys pardalis. Evolutionary considerations.

Amino acid analyses and peptide mapping were performed for the four main haemoglobins from the armoured catfish Pterygoplichthys pardalis; component I, which is functionally distinct from the others, is structurally unique, whereas components II, III and IV, functionally indistinguishable, are closely related in structure. Compositional difference indices are calculated for the four components and for the two major haemoglobins from the trout Salmo irideus, and the results are discussed in terms of structural relationships and evolutionary history of fish haemoglobins.

Amino Acids↗
PubMed1981

Purification and properties of bovine caeruloplasmin.

A novel method is reported for isolation of bovine caeruloplasmin from plasma; it involves a rapid and mild procedure, namely two column chromatographies with stepwise elution and one (NH4)2SO4 precipitation, and results in a proteolytically undegraded homogeneous protein. The general structure of the protein, as evaluated by molecular-weight determination and amino acid composition, is very similar to that established for human and rat caeruloplasmin. Copper determination and e.p.r. spectral analysis on the native and NO-treated protein gave a metal-to-protein stoichiometry of six atoms of copper per molecule. Three copper atoms were detectable by e.p.r., with Type 2/Type 1 ratio = 1 : 3 in most samples. The protein is very sensitive to storage and/or handling. A component was isolated from aged samples, which was found to contain approximately four copper atoms per 125000 daltons, two of which were detectable by e.p.r. with the characters of Type 2 copper. However, the same component was found to be present, although to a lesser extent, in the fresh preparation and does not seem to be related to proteolytic degradation. This component has no oxidase activity. On the basis of these results it is suggested that caeruloplasmin molecules are intrinsically heterogeneous with respect to both copper content and copper type, and this can explain the intriguing stoichiometry regarding the different types of copper centres.

Amino Acids↗
PubMed1981

Purification and functional properties of the hemoglobin components from the rat (Wistar).

Homogeneous components of Wistar rat hemoglobin have been isolated and characterized from the molecular and functional point of view. The O2 equilibrium behaviour of the three main components (HbII, HbIII, HbIVA) has been investigated as a function of pH and organic phosphate concentration. The ligand-binding kinetics of the isolated components have been also studied and are fully consistent with their equilibrium behaviour. It should be remarked that the choice of the system was governed largely by the ability of rat hemoglobins to crystallize very quickly. This almost unique molecular property together with the complete reversibility of the process may allow information to be obtained on the thermodynamics of ligand-linked phase changes.

Animals↗
PubMed1980

Different reactivity of mitochondrial and cytoplasmic aspartate aminotransferases toward an affinity labeling reagent analog of the coenzyme.

The two isoenzymes of aspartate aminotransferase from pig heart have been reacted with a derivative of the coenzyme, 4'-N-(2,4-dinitro-5-fluorophenyl) pyridoxamine-5'-phosphate, which is a potential affinity labeling reagent. The derivative has a great affinity for both isoapoenzymes. In the cytosolic isoenzyme, the reversible binding is followed by a covalent labeling of the epsilon amino group of lysine 258, which usually forms an aldimine bond with pyridoxal-5'-phosphate. In the mitochondrial isoenzyme, no labeling occurs at the active site. The different reactivity indicates that a small but definite difference exists in the geometry of the two active sites. In the cytosolic isoenzyme also a sulfhydryl group outside the active site region, namely cysteine 45, reacts, but not by an affinity labeling mechanism. In both isoenzymes, the reversibly bound reagent slowly undergoes a splitting reaction by which pyridoxal-5'-phosphate is regenerated and activity re-established; the rate of this reaction is not fast enough to impaire the labeling potential of the reagent.

Affinity Labels↗