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L P Visentin

Publications and source records attributed to L P Visentin.

At least 37 records · Page 2Linked to original sources
PubMed1977

Mitogenic activity of Neisseria gonorrhoeae surface antigens in mouse splenic lymphocyte culture.

The mitogenic effects of Neisseria gonorrhoeae endotoxin, fractionated envelope componenents, and intact cells were examined on unsensitized mouse splenic lymphocytes in vitro. The stimulatory effect of these substances was measured by increased [3H]thymidine incorporation in spleen cell cultures. Intact cells, purified lipopolysaccharide (LPS), and cell envelope preparations were highly stimulatory and the stimulation index was dose dependent. Fractionated components of the envelope demonstrated variable stimulation when tested at identical LPS concentrations, reflecting the mitogenic activity of the protein moieties. The stimulatory dose responses for purified N. gonorrhoeae and Escherichia coli LPS were compared and mitogenicity was higher with gonococcal LPS at all concentrations tested. Alkaline detoxification or succinylation of N. gonorrhoeae LPS results in loss of ability to induce blast transformation. The mitogenicity of cell-surface components of N. gonorrhoeae is discussed in terms of LPS and protein content.

Animals↗
PubMed1976

Ribosomal RNA: the message or matrix for ribosomal proteins.

The known nucleotide sequence of Escherichia coli 16S ribosomal RNA has been converted to amino acid sequences in all possible ways, and compared to known ribosomal protein sequences. The degree of similarity is precisely what one would expect by chance alone, providing additional evidence that ribosomal proteins cannot be coded for by ribosomal RNA.

Amino Acid Sequence↗
PubMed1975

Temperature related alterations in the acidic alanine-rich "A" protein from the 50S ribosomal particle of the extreme halophile, Halobacterium cutirubrum.

50-S ribosomal subunits from the extreme halophilic bacterium, Halobacterium cutirubrum, contain an alanine-rich acidic "A" protein which resembles the L7--L12 multimer (Kaltschmidt and Wittmann, 1970) found in the 50-S ribosomal subunit of Escherichia coli cells. The protein contains 24 mole % alanine and is devoid of histidine, tryptophan and cysteine. Unlike E. coli which has two forms of the "A" protein distinguished solely by the acetylation state of the serine amino terminus. H. cutirubrum 50-S subunits contain only one unsubstituted form of the "A" protein in vivo. However, during purification of ribosomes from cells grown between 25 and 37 degrees C the latter "A" protein undergoes rapid, specific, in vitro enzymatic alteration at its carboxy-terminal end. When the halophile is grown in the temperature range of 40 to 42 degrees C the cleaving enzyme is not active and only one form of the "A" protein is found on the ribosomes.

Alanine↗
PubMed1975

Ion effects on protein-nucleic acid interactions: the disassembly of the 50-S ribosomal subunit from the halophilic bacterium, Halobacterium cutirubrum.

The 50-S ribosomal subunits from the extreme halophilic bacterium, Halo-bacterium cutirubrum, stable structurally and functionally in concentrated salt solutions were subjected to ionic environments depleted in either K+ or Mg2+ or both. Under these conditions specific classes of proteins are released from the subunit along with the 5 S RNA. Two-dimensional electrophoretic analysis of the resultant split protein fractions indicate some mutually exclusive effects of specific ions on the binding of specific proteins to the 23 S RNA as well as on the retention of 5 S RNA within the ribosomal macrostructure.

Bacterial Proteins↗
PubMed1975

A chemical approach to the fine structure of biomolecular complexes: the amino terminal region of the 50S ribosomal "A" protein from Bacillus stearothermophilus.

An experimental approach and methodology are described for determining the reactive properties and ionization constants of individual functional groups of proteins within biomolecular complexes. The ionization constants and reactivities of the methionyl-l amino terminus and the lysyl-3 residue of the alanine rich 50S ribosomal "A" protein from Bacillus stearothermophilus have been determined by an extension of the competitive labeling technique used by H. Kaplan, K. J. Stevenson, and B. S. Hartley ((1971), Biochem. J. 124, 289-299). This approach employs (1-14C)- and (3H)acetic anhydride in a double-labeling procedure. In 0.1 M KCl-0.02 M Mg2+-0.05 M Veronal at 10 degrees the methionyl-l amino terminus has a pKa of 7.5 and is exposed on the surface of the ribosome. The lysyl-3 has a pKa of 10 and is also exposed to solvent at the surface of the 50S subunit. Based on a linear free energy relationship (Bronsted plot) obtained with a series of standard amines the methionyl amino terminus has a substantially higher reactivity than expected from its ionization constant. The lysyl epsilon-amino group has the expected reactivity. The abnormally high reactivity of the methionyl amino terminus can only be accounted for by a specific interaction with other functional groups in the ribosome. These data support the proposal that the charged state of this residue is important in the structure and function of the "A" protein at the surface of the ribosome.

Bacillus↗
PubMed1975

Carboxyl-terminal sequences of procaryotic ribosomal proteins from Escherichia coli, Bacillus stearothermophilus, and Halobacterium cutirubrum.

The carboxyl-terminal amino acid sequences of two ribosomal proteins, Escherichia coli L12 and E. coli S4, and the proteins believed to be their equivalents from Bacillus stearothermophilus and Halobacterium cutirubrum, were determined. These proteins are known to be required for peptide chain termination (L12) and in ribosome assembly (S4). The carboxyl-terminal sequences obtained suggest that the E. coli and B. stearothermophilus proteins have retained structural homology in this region, whereas the H. cutirubrum proteins have not.

Amino Acid Sequence↗
PubMed1975

The conservation of amino acids in the n-terminal position of ribosomal and cytosol proteins from Escherichia coli, Bacillus stearothermophilus, and Halobacterium cutirubrum.

Alanine, methionine, and serine are the predominant N-terminal residues in the cytosol and ribosomal protein fractions from the thermophile Bacillus stear othermophilus and the extreme halophile Halobacterium cutirubrum, a similar situation to that previously found in Escherichia coli. In all three bacteria the N-terminal residues of the 30S ribosomal proteins are mainly alanine greater than methionine greater than serine whereas in the 50S ribosomal proteins from E. coli and B. stearothermophilus the predominant residues are methionine greater than alanine greater than serine suggesting conservation of specific N-terminal residues in these ribosomal proteins. However, the 50S ribosomal proteins from H. cutirubrum showed serine as the major N-terminal residue.

Amino Acid Sequence↗
PubMed1972

Halobacterium cutirubrum ribosomes. Properties of the ribosomal proteins and ribonucleic acid.

1. The 30S ribosomal subunit of the extreme halophile Halobacterium cutirubrum is unstable and loses 75% of its ribosomal protein when the 70S ribosome is dissociated into the two subunits. A stable 30S subunit is obtained if the dissociation of the 70S particle is carried out in the presence of the soluble fraction. 2. A fractionation procedure was developed for the selective removal of groups of proteins from the 30S and 50S subunits. When the ribosomes, which are stable in 4m-K(+) and 0.1m-Mg(2+), were extracted with low-ionic-strength buffer 75-80% of the 30S proteins and 60-65% of the 50S proteins as well as the 5S rRNA were released. The proteins in this fraction are the most acidic of the H. cutirubrum ribosomal proteins. Further extraction with Li(+)-EDTA releases additional protein, leaving a core particle containing either 16S rRNA or 23S rRNA and about 5% of the total ribosomal protein. The amino acid composition, mobility on polyacrylamide gels at pH4.5 and 8.7, and the molecular-weight distribution of the various protein fractions were determined. 3. The s values of the rRNA are 5S, 16S and 23S. The C+G contents of the 16S and 23S rRNA were 56.1 and 58.8% respectively and these are higher than C+G contents of the corresponding Escherichia coli rRNA (53.8 and 54.1%).

Amino Acids↗