Biomedical subjects

S Altamura

Publications and source records attributed to S Altamura.

26 records · Page 2Linked to original sources

PubMed1989

Gastrin-releasing peptide-like immunoreactivity in porcine follicular fluid and ovary.

Porcine follicular fluid was found to contain gastrin-releasing peptide (GRP) by radioimmunoassay. High pressure liquid chromatography of the extracted material showed two peaks of GRP immunoreactivity that closely resembled the C-terminal fragments of GRP, GRP18-27 and GRP14-27. Immunohistochemical studies revealed specific staining for GRP in the granulosa cells of adult porcine ovary. These results demonstrate the presence of substances which behave like authentic GRP-like peptides in porcine ovary and follicular fluid and suggest that these peptides may play a paracrine and/or autocrine role in the regulation of the ovarian function.

Animals↗

PubMed1989

Identification of immunoreactive gastrin-releasing peptide related substances in adult rat Leydig cells.

Purified adult rat Leydig cells were found to produce gastrin-releasing peptide (GRP) by radioimmunoassay (RIA). Gel chromatography of the extracted material showed a single peak of GRP immunoreactivity. Further high pressure liquid chromatography (HPLC) analysis resolved the extract into two peaks that closely resembled the C-terminal fragment of GRP, GRP18-27 and GRP14-27. Immunohistochemical studies revealed specific staining for GRP in the Leydig cells of adult rat testis. These results demonstrate, by a number of independent criteria, that rat Leydig cells contain substances which behave like authentic GRP-like peptides. Since the peptides appear to be of local origin, a paracrine function within the rat testis is suggested.

Animals↗

PubMed1988

Aminoglycoside-induced mistranslation in thermophilic archaebacteria.

The effect of selected aminoglycoside antibiotics on the translational accuracy of poly(U) programmed ribosomes derived from the thermophilic archaebacteria Thermoplasma acidophilum, Sulfolobus solfataricus, Thermococcus celer and Desulfurococcus mobilis has been determined. Under optimum temperature and ionic conditions for polyphenylalanine synthesis, the four species investigated are found to be markedly diverse in their response to the miscoding-inducing action of aminoglycoside antibiotics. T. acidophilum is sensitive to all of the compounds tested except streptomycin; S. solfataricus responds to paromomycin and to hygromycin B; T. celer is only affected by neomycin, and D. mobilis is refractory to all drugs. The only feature shared by the four species under study, and by all archaebacteria so far investigated, is their complete insensitivity to streptomycin. The structural and phylogenetic implications of the remarkable diversity encountered among archaebacterial ribosomes in their susceptibility to aminoglycosides are discussed.

Anti-Bacterial Agents↗

PubMed1988

Ribosomes of the extremely thermophilic eubacterium Thermotoga maritima are uniquely insensitive to the miscoding-inducing action of aminoglycoside antibiotics.

Poly(U)- and poly(UG)-programmed cell-free systems were developed from the extreme thermophilic, anaerobic eubacterium Thermotoga maritima, and their susceptibility to aminoglycoside and other antibiotics was assayed at a temperature (75 degrees C) close to the physiological optimum (80 degrees C) for cell growth and in vitro polypeptide synthesis, using a Bacillus stearothermophilus system as the reference. The synthetic capacity of the Thermotoga assay mixture was abolished by the eubacterium-targeted drugs chloramphenicol, thiostrepton, and kirromycin. However, streptomycin, the disubstituted 2-deoxystreptamines (kanamycin, gentamicin, neomycin, and paromomycin), and the monosubstituted 2-deoxystreptamine (hygromycin) all failed to promote translational misreading of poly(U) on Thermotoga ribosomes; they also failed to block polyphenylalanine synthesis at a low (less than 10(-4) M) concentration and did not inhibit Thermotoga cell growth at a high (10 micrograms/ml) concentration even though Thermotoga ribosomes possess the 16S rRNA sequences required for aminoglycoside action. In contrast to the other eubacteria, Thermotoga elongation factor G was also refractory to the steroid inhibitor of peptidyl-tRNA translocation fusidic acid.

Aminoglycosides↗

PubMed1986

Archaebacterial and eukaryotic ribosomal subunits can form active hybrid ribosomes.

Purified ribosomal subunits from the extremely thermoacidophilic archaebacterium Sulfolobus solfataricus are able to recognize ribosomal subunits from the yeast Saccharomyces cerevisiae forming hybrid monosomes that can be revealed by sucrose gradient analysis and are active in peptide bond formation. Both reciprocal combinations (archaebacterial 30 S + eukaryotic 60 S and archaebacterial 50 S + eukaryotic 40 S) are functional. In contrast, no hybrid couples are formed between subunits of yeast and Escherichia coli ribosomes. These results indicate that ribosomes of at least one archaebacterial species share specific structural features with those of the lower eukaryote S. cerevisiae.

Archaea↗

PubMed1986

Differential features of ribosomes and of poly(U)-programmed cell-free systems derived from sulphur-dependent archaebacterial species.

The properties of poly(U)-directed cell-free systems developed from the sulphur-dependent, thermophilic archaebacteria Desulfurococcus mobilis, Thermoproteus tenax, Sulfolobus solfataricus, Thermococcus celer and Thermoplasma acidophilum have been compared. All systems are truly thermophilic in requiring incubation at temperatures close to the physiological optimum for cell growth. Under optimized conditions the error frequency in tRNA selection is less than 0.4% at 80 degrees C, and synthetic efficiencies (Phe residues polymerized per ribosome in 40 min) span from 4 for Tp. tenax, to 10 for Tc. celer, to 20-25 for D. mobilis and T. acidophilum and to 40 for S. solfataricus. According to requirements for polypeptide synthesis and to degree of stability of the ribosomal subunits' association, sulphur-dependent thermophiles cluster into two groups. Group I organisms (D. mobilis, Tp. tenax, S. solfataricus) harbour 70-S monomers composed of weakly associated subunits, whose poly(Phe)-synthesizing capacity is totally dependent on added spermine while being drastically inhibited by monovalent cations. Group II organisms (Tc. celer and T. acidophilum) contain 70-S particles composed of tightly bonded subunits, whose synthetic capacity is independent of spermine while being totally dependent on monovalent cations. Spermine promotes poly(Phe) synthesis on ribosomes of group I organisms by converting the peptidyltransferase center into an active conformation, while monovalent cations are inhibitory by preventing the interaction between the free ribosomal subunits. The closeness between Tc. celer and T. acidophilum ribosomes provides new insight on the phylogenetic placement of Thermococcaceae.

Archaea↗

PubMed1986

Unique antibiotic sensitivity of archaebacterial polypeptide elongation factors.

The antibiotic sensitivity of the archaebacterial factors catalyzing the binding of aminoacyl-tRNA to ribosomes (elongation factor Tu [EF-Tu] for eubacteria and elongation factor 1 [EF1] for eucaryotes) and the translocation of peptidyl-tRNA (elongation factor G [EF-G] for eubacteria and elongation factor 2 [EF2] for eucaryotes) was investigated by using two EF-Tu and EF1 [EF-Tu(EF1)]-targeted drugs, kirromycin and pulvomycin, and the EF-G and EF2 [EF-G(EF2)]-targeted drug fusidic acid. The interaction of the inhibitors with the target factors was monitored by using polyphenylalanine-synthesizing cell-free systems. A survey of methanogenic, halophilic, and sulfur-dependent archaebacteria showed that elongation factors of organisms belonging to the methanogenic-halophilic and sulfur-dependent branches of the "third kingdom" exhibit different antibiotic sensitivity spectra. Namely, the methanobacterial-halobacterial EF-Tu(EF1)-equivalent protein was found to be sensitive to pulvomycin but insensitive to kirromycin, whereas the methanobacterial-halobacterial EF-G(EF2)-equivalent protein was found to be sensitive to fusidic acid. By contrast, sulfur-dependent thermophiles were unaffected by all three antibiotics, with two exceptions; Thermococcus celer, whose EF-Tu(EF1)-equivalent factor was blocked by pulvomycin, and Thermoproteus tenax, whose EF-G(EF2)-equivalent factor was sensitive to fusidic acid. On the whole, the results revealed a remarkable intralineage heterogeneity of elongation factors not encountered within each of the two reference (eubacterial and eucaryotic) kingdoms.

Aminoglycosides↗

PubMedDate not supplied

A Multimeric Synthetic Peptide Combinatorial Library.

We describe here a novel type of synthetic peptide library, named Multimeric Synthetic Peptide Combinatorial Library (M-SPCL), where multiple small peptide ligands are tied together in the same molecule. The advantage of using small peptides in the form of M-SPCL is two-fold: first, the high density assembly of the sequences on the branching scaffold leads to signal amplification, thereby effectively lowering the binding threshold for the selection of ligands; second, to interfere with protein-protein interactions, multimericity has been shown to be a desirable feature per se. The M-SPCL is prepared by solid-phase peptide synthesis, based on the structure of Multiple Antigen Peptides. When prepared in Positional Scanning format [C. Pinilla, J. Appel, P. Blanc and R.A. Houghten. 1992. BioTechniques 13: 901-905], selection is based on the amplified interaction of a single residue in a sequence-defined position. The usefulness of the new library was demonstrated by the selection of octameric peptides, which inhibit the binding of the cytokine human interleukin-6 to its receptor, with an apparent nanomolar affinity. Tetrameric, but not dimeric, branched peptides with the same sequences were also active with comparable affinity. The success of this approach is noteworthy, since screening of the corresponding monomeric pentapeptide SPCL did not lead to the selection of any inhibitory compound in the same system.

Amino Acid Sequence↗