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Biomedical subjects

F Bossa

Publications and source records attributed to F Bossa.

At least 127 records · Page 7Linked to original sources
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↗
PubMed1978

Primary structure of hemoglobin from trout (Salmo irideus). Amino acid sequence of alpha chain of Hb trout I.

The amino acid sequence of the alpha chain of the hemoglobin component of trout's blood which is devoid of heterotropyc phenomena, i.e. Hb trout I, is presented. The sequence has been determined by analyzing the soluble tryptic peptides obtained from the whole globin and the peptides obtained after redigesting the insoluble 'core' with chymotrypsin. Alignment of the peptides with the structure of human as well as carp and Catostomus clarkii alpha chains shows that Hb trout I alpha chain differs from the corresponding human protein by 43% amino acid substitutions and from the two other fish by 34.5% and 33.1%, respectively. Further comparison of sequence data available for the N-terminal region suggests that the divergence between Hb trout I and IV, the other major hemoglobin component of trout's blood, is greater than that found between each trout hemoglobin and the other two fishes (carp and C. clarkii.).

Amino Acid Sequence↗
PubMed1977

Low molecular weight peptides controlling transcription are present in the calf thymus chromatin structure.

A calf thymus peptide fraction controlling DNA and chromatin template has been purified by DNA-cellulose and Dowex 50 WX2 chromatography and its amino acid composition determined. The active peptide fraction can be extracted in high pH buffer from calf thymus native chromatin previously deproteinized by chloroform-isamyl alcohol and phenol. These data demonstrate that the thymic peptide(s) is (are) a chromatin protein constituent strongly linked to DNA. The specificity in association of the peptide(s) to DNA has also been considered.

Animals↗
PubMed1976

Serine transhydroxymethylase from rabbit liver. Sequence of anonapeptide at the pyridoxal-5'-phosphate-binding site.

The amino acid sequence of the coenzyme-binding site of serine transhydroxymethylase from rabbit liver has been determined. After reduction with NaBH4 and aminoethylation, a first sample of enzyme was digested with thermolysin and a single phosphopyridoxyl peptide was isolated. A second sample of similarly treated enzyme was digested with chymotrypsin and three phosphopyridoxyl peptides clearly originating from a unique coenzyme-binding site were isolated. Sequence analysis of these peptides indicate the following structure: Val-Val-Thr-Thr-His(Pxy)-Thr-Leu. Sequence homologies of the active site of various pyridoxalphosphate enzymes are discussed in terms of a possible catalytic role and of evolution of this class of proteins.

Amino Acid Sequence↗
PubMed1976

Large-scale purification and some properties of the mitochondrial aspartate aminotransferase from pig heart.

A method has been developed which allows isolation of 0.3--0.5 g of mitochondrial aspartate aminotransferase in five days starting from 10 pig hearts; the method does not involve initial preparation of mitochondria. Mitochondrial malate dehydrogenase and the cytoplasmic aspartate aminotransferase may conveniently be recovered from side fractions. The product mitochondrial aspartate aminotransferase is homogeneous as judged by various electrophoretic techniques and by N-terminal analysis. Crystals of the enzyme have been obtained both from concentrated, essentially salt-free, solutions and from solutions of ammonium sulphate. The amino acid composition, N and C-terminal amino acid sequences and subunit molecular weight have been determined; these characteristic properties are compared with those of the cytoplasmic isozyme from the same source.

Amino Acid Sequence↗
PubMed1976

The phosphopyridoxyl peptide from the mitochondrial aspartate aminotransferase of beef kidney.

The sequence around the coenzyme-binding lysine of mitochondrial aspartate amino-transferase from beef kidney was determined. The holoenzyme was treated with NaB3H4 and digested with thermolysin; the labelled peptide was isolated and its sequence proved to be identical with sequences around the coenzyme site from the same isoenzyme of different organs and animals (pig heart and sheep liver). The sequences of the phosphopyridoxyl peptides of the mitochondrial aspartate aminotransferases appear to be closely related to the corresponding peptides from the cytoplasmic isoenzymes.

Amino Acids↗