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F Bossa

Publications and source records attributed to F Bossa.

At least 109 records · Page 6Linked to original sources
PubMed1984

Structural and genetic relationships between cytosolic and mitochondrial isoenzymes.

The most common type of genetic relationship between cytosolic and mitochondrial isoenzymes will probably be found to be divergent evolution from a common ancestral form. This is firmly established for the aspartate aminotransferases and less directly so in other cases. The two isoenzymes of aspartate aminotransferase have evolved at roughly equal rates at the level of total amino acid sequence but certain limited surface regions of the mitochondrial form have been much more highly conserved than corresponding regions in the cytosolic protein; these regions probably play a role in topogenesis of the mitochondrial isoenzyme. It is of interest that nearly all mitochondrial proteins are initially synthesised as precursors of molecular weight greater than the mature forms. In the case of aspartate aminotransferase, and possibly of other such isoenzymes, the N-terminus of the mature protein is nearly coincident with that of the cytosolic isoenzyme. Hence during evolution either the gene for the mitochondrial isoenzyme has gained an extra coding region for this N-terminal extension or, less likely, the structural gene for the cytosolic form has suffered a sizeable terminal deletion. Cytosolic and mitochondrial superoxide dismutases have not shared a common ancestral form as shown by the fact that their primary structures are completely unrelated. On the other hand, the mitochondrial and prokaryotic enzymes are clearly related. There is now, however, evidence to suggest that some prokaryotes possess a copper/zinc enzyme related to the eukaryotic cytosolic form. Hence the possibility arises that primitive prokaryotes possessed both proteins. The copper/zinc superoxide dismutase has been retained in the cytosol of eukaryotic cells and a few bacterial species.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
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

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

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↗
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↗
PubMed1982

Succinylated copper, zinc superoxide dismutase. A novel approach to the problem of active subunits.

Bovine erythrocyte superoxide dismutase (BESOD) has been extensively succinylated with succinic anhydride. Succinylated BESOD has an identical electron paramagnetic resonance (EPR) spectrum but only 10% as much activity as the native enzyme, showing that an increase of the negative charge of the protein surface lowers the activity without alteration of the active site structure. On the other hand, sodium dodecyl sulfate (NaDodSO4)-polyacrylamide gel electrophoresis indicates that interaction between subunits is strongly weakened by succinylation. NaDodSO4 has no effect on either the activity or EPR spectrum of the protein. BESOD was immobilized by coupling to a Sepharose matrix with no alteration of the EPR spectrum. Succinylation of the immobilized protein led to detachment from the gel of approximately 50% of the molecules, as estimated by parallel EPR measurements of the gel and activity determinations on the eluate. It is concluded the succinylation leads to dissociation of BESOD into nondenatured subunits, having lower activity than the native protein possibly because of charge effects on the enzyme-O2-interaction.

Animals↗
PubMed1980

Evidence for a sulfhydryl group at the active site of serine transhydroxymethylase.

Iodoacetate reacts rapidly with one sulfhydryl group/subunit on aposerine transhydroxymethylase. The carboxymethylated apoenzyme does not recombine with pyridoxal 5'-phosphate. Under conditions used in the apoenzyme studies, the holoenzyme does not react to an appreciable extent with iodoacetate. The reaction of the apoenzyme with iodoacetate shows pseudo-first order kinetics with a half-life of about 3 min at 0 degrees C and pH 7.0. A pattern of saturation kinetics was found when increasing concentrations of iodoacetate were used. The half-maximum rate of inactivation occurred at 1.5 mM iodoacetate. Phosphate was observed to inhibit competitively the inactivation by iodoacetate with a Ki value of 1.8 mM. No inactivation of aposerine transhydroxymethylase was found when iodoacetamide was used in place of iodoacetate. These experiments suggest that removal of the pyridoxal 5'-phosphate from serine transhydroxymethylase exposes a reactive sulfhydryl group with a nearby cationic center which binds the carboxyl group of iodoacetate. The reactive sulfhydryl group was labeled with [14C]iodoacetate. From a chymotryptic digest, a 14C-containing peptide was isolated and determined to be: His-Pro-Lys-Leu-Ile-Ile-Ala-Gly-Thr-Ser-Cys(Cm)-Tyr.

Binding Sites↗