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Biomedical subjects

G Barabás

Publications and source records attributed to G Barabás.

16 recordsLinked to original sources
PubMed1994

Modification of glutamine synthetase in Streptomyces griseus by ADP-ribosylation and adenylylation.

Addition of NH4+ to STreptomyces griseus 2682 cells grown in NO3- containing medium resulted in a rapid decline in glutamine synthetase activity due to covalent modification of the enzyme. The NH4+ promoted inactivation of the enzyme was inhibited by the ADP-ribosyltransferase inhibitor 3-methoxybenzamide. In the presence of ADP-ribosyltransferase activity the purified glutamine synthetase was also inhibited by NAD+ in a concentration-dependent manner. ADP-ribosylation of glutamine synthetase was demonstrated in vitro by showing the incorporation of labeled ADP-ribose from [alpha-32P]NAD+ into glutamine synthetase subunits. Beside ADP-ribosylation, adenylylation of glutamine synthetase was also shown in S. griseus since phosphodiesterase I treatment reactivated the enzyme in crude extracts of NH(4+)-shocked cells. Glutamine synthetase was also inhibited and modified by ATP in crude cellular extracts. These results suggest that in S. griseus 2682 ADP-ribosylation of glutamine synthetase could be an alternative modification to adenylylation to regulate glutamine synthetase activity.

Adenine Phosphoribosyltransferase↗
PubMed1992

Transmembrane signaling changes with aging.

Altered immune response and transmembrane signaling with aging has previously been demonstrated. The aim of the present study was to characterize PMNLs and lymphocyte G proteins and to determine whether their relative amounts are altered with aging. First we studied the effects of FMLP on PMNLs IP3 formation. It was found that in any group of elderly the PMNLs IP3 formation was significantly decreased compared to that of young subjects. In FMLP receptor binding affinity no measurable difference exists in either low- or high-affinity FMLP receptors. The autoradiogram of 32P-ADP-ribosylated proteins by CT in lymphocytes of young individuals showed a major polypeptide of 40 kDa, and two much less prevalent components of 52 and 45 kDa. In contrast, in lymphocytes of elderly subjects the major polypeptide was 45 kDa, and the two others were very weakly labeled. In PMNLs, CT labeled the 45-kDa band quite strongly, mainly in the elderly, and the 52- and 40-kDa bands were very weakly labeled, mainly in young subjects. When PT was used, no age-related pattern changes could be demonstrated, while differences could be observed between the two types of cells.

Adenosine Diphosphate Ribose↗
PubMed1992

The possible role of ADP ribosylation in physiological regulation of sporulation in Streptomyces griseus.

The role of ADP ribosylation of proteins in the physiological regulation of sporulation in Streptomyces griseus was studied. We report here that both the activity of NAD+: arginine ADP-ribosyltransferase (ADPRT) and the pattern of ADP-ribosylated proteins showed characteristic changes during the life cycle in S. griseus 2682. Analysis off ADP-ribosylated proteins revealed that in a nonsporulating mutant of the parental wild-type (wt) strain (Bld7 mutant), both the activity of ADPRT and the pattern of ADP-ribosylated proteins were different from those of the parental strain. Addition of 3-aminobenzamide (3AB), the most potent inhibitor of ADPRT, inhibited sporulation of S. griseus 2682 and the A-factor (AF)-induced sporulation of S. griseus Bld7, but in both cases the inhibitory effect of 3AB was strictly age-dependent. Using [alpha-32P]GTP, we have demonstrated the presence of GTP-binding proteins in purified cell membranes of S. griseus 2682 and S. griseus Bld7. The same GTP-binding proteins were observed in Bld7 and the wt. AF stimulated the basal GTPase activity of cell membranes of S. griseus 2682 in a concentration-dependent manner, suggesting that GTP-binding proteins might be involved in the AF-induced sporulation process.

Adenosine Diphosphate↗
PubMed1990

ADP-ribosylation of membrane proteins of Streptomyces griseus strain 52-1.

Membranes purified from cells of Streptomyces griseus strain 52-1 possess an ADP-ribosyltransferase activity. The enzyme transfers the ADP-ribose moiety of NAD to one major membrane protein of Mr 32,000 and 2-3 minor proteins of larger molecular weights. The effects of inhibitors on the ADP-ribosyltransferase activity proves that the reaction is enzymatic and suggests that the enzyme ADP-ribosylates the guanidine group of arginine. The kinetics of liberation of ADP-ribose during alkaline hydrolysis of the modified proteins is consistent with the arginine-ADP-ribose bond. This is the first report of ADP-ribosylation of proteins in a Gram-positive bacterium.

Bacterial Proteins↗
PubMed1990

Effect of aminoglycoside antibiotics on the autolytic enzyme of Streptomyces griseus.

The isolated cell wall of Streptomyces griseus 52-1 strain labelled with fluorescein isothiocyanate (FITC) and containing wall-bound autolytic enzyme was lysed as a function of different cations. The autolysis was accelerated by aminoglycoside antibiotics (streptomycin and the structurally closely related neomycin) which have a polycationic character. Since this strain is a streptomycin producer it is suggested that streptomycin may have a regulatory function on autolysis.

Amidohydrolases↗
PubMed1990

In vitro investigation of BK-218, a new oral and parenteral cephalosporin.

The antibacterial activity of BK-218 was similar to that of cefamandole when it was tested against several laboratory strains. The inhibiting effect of BK-218 was greater than that of cephalexin and cefoxitin on penicillin-binding proteins of Escherichia coli HB101. This result was in close correlation with the relative inhibition of radiolabeled glucosamine incorporation (greatest with BK-218) and with the lytic effect (most intensive with BK-218). BK-218 proved to be a good inhibitor for all five of the beta-lactamases that were investigated, although two enzymes (Enterobacter cloacae P99 and Pseudomonas aeruginosa Cilote) hydrolyzed it to some extent.

Bacteria↗
PubMed1989

Production of a streptomycin-Park nucleotide complex by Streptomyces griseus.

A compound (compound X) with antibacterial activity was isolated from early-exponential-phase cultures of the streptomycin producer Streptomyces griseus and from protoplast cultures of the same strain. The protoplast cultures produced a larger amount of compound X than did the young hyphae. Both the mycelia and the protoplasts incorporated 14C-labeled myo-inositol, a precursor of streptomycin, into compound X, which has an amino acid content related to that of the cell wall peptidoglycan of the producer strain. Compound X may contain a streptomycin molecule covalently bound to a cell wall precursor unit, i.e., to a Park nucleotide (J. T. Park, J. Biol. Chem. 194:897-904, 1952), through the glutamic acid of the pentapeptide component.

Anti-Bacterial Agents↗
PubMed1985

Possible role of streptomycin released from spore cell wall of Streptomyces griseus.

Vegetative mycelia and spores of the investigated high- and low-producer strains of Streptomyces griseus bound significant amounts (4%) of streptomycin, which could be removed by increasing ionic strength. The release of antibiotic from the spores was easier when the spores were germinating. This phenomenon is considered to play an ecological role. We suppose that the streptomycin released during the germination process may protect the young hyphae from the different bacteria growing in the microenvironment of the Streptomyces spores.

Cell Wall↗