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Biomedical subjects

A Gambacorta

Publications and source records attributed to A Gambacorta.

84 records · Page 5Linked to original sources
PubMed1976

DNA-dependent RNA polymerase from the thermophilic bacterium Caldariella acidophila. Purification and basic properties of the enzyme.

A DNA-dependent RNA polymerase has been isolated from Caldariella acidophila, a thermophilic bacterium living in acidic hot springs at temperatures ranging from 63 to 89 degrees C. The enzyme was purified 180-fold and is composed of five different subunits having the following molecular weights: a = 127000, b = 120000, c = 72000, d = 65000, and e = 38000. The enzyme is activated by Mn2+ and Mg2+ and exhibits optimal activity in the presence of 0.5 mM Mn2+. The activity depends on ionic strength, with a maximum at 0.25 M KCl, and exhibits a pH optimum at 7.8 in the presence of Tris-HCl buffer. The enzyme shows a high degree of thermophilicity, its temperature optimum being 80 degrees C in the in vitro assay. The thermophilicity of C. acidophila RNA polymerase allows studies on enzyme-template interactions to be performed in a temperature range where many templates are close to their Tm.

Bacteria↗
PubMed1976

Stable, inducible thermoacidophilic alpha-amylase from Bacillus acidocaldarius.

Bacillus acidocaldarius Agnano 101 produces an inducible thermoacidophilic alpha-amylase. The enzyme production occurs during the stationary phase of growth in the presence of compounds with alpha-1,4-glucosidic linkages. The enzymatic activity is both present in the culture medium and associated with the cells; the enzymes purified from both sources show identical molecular and catalytic properties. The purified amylase has a single polypeptide chain of molecular weight 68,000 and behaves like an alpha-amylase with affinity constants for starch and related substances of 0.8 to 0.9 mg/ml. The pH and temperature optima for activity are 3.5 and 75degreesC, respectively. The amylase is stable at acidic pH (below 4.5). Its thermal stability is strictly dependent upon protein concentration; the half-life at 60degreesC of the amylase in a 70-mug/ml solution is about 5 days.

Amylases↗
PubMed1975

Extremely thermophilic acidophilic bacteria convergent with Sulfolobus acidocaldarius.

A series of extremely thermophilic acidophilic bacteria has been characterized as closely resembling the species Sulfolobus acidocaldarius except for a totally different guanosine-cytosine content in the DNA; some conceptual consequences of this situation are discussed. Both organisms also share special features, including a very characteristic type of ether lipid, with other extreme acidophilic thermophiles.

Acetates↗
PubMed1975

Ultrastructure of an extremely thermophilic acidophilic micro-organism.

A thermoacidophilic micro-organism, isolated from volcanic hot springs near Naples, was cultivated in vitro, and examined by electron microscopy in sections and after negative staining. The cells were almost spherical, with a diameter of about 0.7 to 1.0 mum. Their morphology was very primitive: the protoplasm was composed only of ground cytoplasm, ribosomes, and randomly distributed DNA strands. They were surrounded by a plasma membrane and by an extracellular coat about 20 nm thick which displayed a regular hexagonal pattern. Cell replication occurred by binary fission with median constriction during which a bipolar localization of nuclear material was observable. The morphology is compared with that of other known micro-organisms living in similar habitats.

Bacteria↗
PubMed1974

Effects of pH and temperature on the fatty acid composition of bacillus acidocaldarius.

The fatty acid composition of lipid extracts from cells of Bacillus acidocaldarius grown at temperatures of 50 to 70 C and pH values of 2 to 5 was determined by gas chromatography of the methyl esters. The most abundant fatty acids are 11-cyclohexylundecanoic and 13-cyclohexyltridecanoic, followed by anteiso- and iso-heptadecanoic; unsaturated acids are absent. Highly aerated cultures produce more of the iso and anteiso acids and less of the cyclohexyl acids. The effects of temperature and pH are interdependent; at lower pH, increasing temperature raises the proportion of the iso and anteiso acids, but at higher pH the effect of increasing temperature is reversed and the proportion of the cyclohexyl acids is increased.

Bacillus↗
PubMed1972

The formation of -cyclohexyl-fatty acids from shikimate in an acidophilic thermophilic bacillus. A new biosynthetic pathway.

Labelled acetate, phenylalanine and shikimic acid were fed to Bacillus acidocaldarius. A high proportion of the (14)C incorporated from acetate and shikimate was recovered in methyl esters from the cell lipids, but such recovery of (14)C from phenylalanine was low. Only the (14)C from shikimate was selectively incorporated into 11-cyclohexylundecanoate and 13-cyclohexyltridecanoate. Degradation of these cyclohexyl-fatty acids showed that shikimate was incorporated as an intact C(7) unit.

Acetates↗
PubMedDate not supplied

Purification and properties of a thermophilic and thermostable DNA polymerase from the archaebacterium Sulfolobus solfataricus.

A DNA-dependent DNA polymerase was obtained in homogenous form from the thermoacidophilic archaebacterium Sulfolobus solfataricus. The enzyme, purified 706-fold, has a molecular mass of about 110000 daltons as determined by gel filtration and by glycerol gradient centrifugation. It requires Mg++ for its activity and has a pH optimum of 7.7. The activity is sharply dependent on the ionic strength. The enzyme is thermostable; its properties and activity requirements were characterized. The features of this enzyme are compared to those of other DNA polymerases isolated either from prokaryotes or eukaryotes.

Archaea↗
PubMedDate not supplied

Properties of the purified elongation factor 2 in the thermoacidophilic archaebacterium Sulfolobus solfataricus.

The elongation factor 2 (aEF-2) has been purified to homogeneity from the extreme thermoacidophilic archaebacterium Sulfolobus solfataricus. It is the only target protein which is ADP-ribosylated by diphtheria toxin in presence of NAD and this modification abolishes its property to support poly(Phe) synthesis in vitro. The factor is constituted by a single polypeptide chain with a relative molecular mass of 78,000 and an isoelectric point of 5.9. aEF-2 is resistant to heat denaturation as shown by the fact that its capability to be ADP-ribosylated was only 10% reduced after 4 h treatment at 80 degrees C. Its amino acid composition does not reveal significant differences with that of analogous factors in other sources; nevertheless, the deviation function indicates that aEF-2 is related to Sulfolobus acidocaldarius and eukaryotes EF-2 more than to eubacterial EF-G or other archaebacterial EF-2.

Adenosine Diphosphate Ribose↗