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R F Goldberger

Publications and source records attributed to R F Goldberger.

At least 37 records · Page 2Linked to original sources
PubMed1972

Specificity of interaction between the first enzyme for histidine biosynthesis and aminoacylated histidine transfer ribonucleic acid.

The specificity of the interaction between phosphoribosyltransferase and partially purified preparations of various species of transfer ribonucleic acid (tRNA) was investigated with the use of a filter binding assay. The enzyme showed a higher affinity for histidyl-tRNA than for arginyl- or glutamyl-tRNA. Competition experiments revealed that the enzyme does not distinguish between the aminoacylated and deacylated forms of arginine tRNA or glutamic acid tRNA, since all the binding of the aminoacylated tRNA could be inhibited by deacylated tRNA. The enzyme does, however, distinguish between the aminoacylated and deacylated forms of histidine tRNA. Approximately 70% of the binding of aminoacylated histidine tRNA is specific, since only 30% of the binding could be inhibited by deacylated tRNA. The possibility that the regulatory role of phosphoribosyltransferase is carried out as a complex with histidyl-tRNA is consistent with these data.

Acylation↗
PubMed1971

Interaction between the first enzyme for histidine biosynthesis and histidyl transfer ribonucleic acid.

Previous studies suggested that phosphoribosyltransferase, which catalyzes the first step of the pathway for histidine biosynthesis in Salmonella typhimurium and which is sensitive to inhibition by histidine, plays a role in repression of the histidine operon. Recently, we showed that the enzyme has a high affinity for histidyl transfer ribonucleic acid (His-tRNA), which is known to participate in the repression process. In the present study, we have investigated further the interaction between the enzyme and His-tRNA. We found that His-tRNA binds at a site on phosphoribosyltransferase distinct from the catalytic site and the histidine-sensitive site; that the substrates of the enzyme inhibit the binding of His-tRNA, whereas histidine does not do so; that, once a complex has been formed between phosphoribosyltransferase and His-tRNA, the substrates of the enzyme decrease the stability of the complex, whereas histidine is without effect; and that purified phosphoribosyltransferase which has a defect in its inhibition by histidine (produced by mutation) displays an altered ability to bind His-tRNA, a finding which may be a reflection of the fact that mutants producing such a defective enzyme display an alteration of the repression process.

Acrylates↗
PubMed1970

Interaction between histidyl transfer ribonucleic acid and the first enzyme for histidine biosynthesis of Salmonella typhimurium.

Previous studies showed that the enzyme (phosphoribosyltransferase) which catalyzes the first step of the histidine pathway in Salmonella typhimurium plays a role in regulation of the histidine operon. Since histidyl transfer ribonucleic acid (His-tRNA) is required for repression of the histidine operon, we considered the possibility that the role of phosphoribosyltransferase might be realized through an interaction with His-tRNA. One prediction inherent in this idea is that the enzyme should interact with His-tRNA in vitro. Evidence is presented for such an interaction. Binding of (3)H-His-tRNA to purified phosphoribosyltransferase was tested on Sephadex columns and on nitrocellulose filters. The enzyme was found to have a high affinity for tRNA. Comparing the binding of (3)H-His-tRNA with that of tRNA aminoacylated with other (3)H-amino acids disclosed that the binding of the histidyl species of tRNA is favored over that of other species and is dependent upon magnesium-ion concentration.

Acrylates↗
PubMed1969

Studies on repression of the histidine operon. II. The role of the first enzyme in control of the histidine system.

Recent studies on repression of the enzymes for histidine bio-synthesis in Salmonella typhimurium demonstrated that the kinetic pattern in which the enzymes become repressed is influenced by the state of the feedback-sensitive site of the first enzyme of the pathway (Kovach et al., J. Bacteriol., 97, 1283 (1969)). In the present study we demonstrate that under certain conditions alteration of the feedback-sensitive site of the first enzyme prevents repression of the histidine operon. We conclude that the first enzyme plays a previously unrecognized role in regulation of the histidine system.

Binding Sites↗
PubMed1969

Repression of the histidine operon: effect of the first enzyme on the kinetics of repression.

Kinetic studies on repression of the enzymes for histidine biosynthesis in Salmonella typhimurium showed that, upon addition of histidine to a derepressed culture, the enzymes became repressed in a temporal sequence which corresponds with the positional sequence of the genes in the histidine operon. This serial pattern of repression occurred under conditions in which the feedback site of the first enzyme for histidine biosynthesis is intact. When this site was rendered nonfunctional the pattern of repression was changed so that all of the enzymes became repressed concomitantly. These results suggest that the first enzyme for histidine biosynthesis plays a hitherto unrecognized role in control of the histidine system.

Enzyme Repression↗
PubMed1969

Kinetics of induction of the lactose operon on an episome in Samonellla typhimurium.

A kinetic study of induction of the enzymes of the lactose operon was carried out under conditions known to affect the kinetics of derepression of the enzymes of the histidine operon. The results show that the lactose system is similar to the histidine system in its responsiveness to conditions thought to affect the formylating capacity of the cell. This was demonstrated in the following ways: (i) trimethoprim, which is known to reduce the formylating capacity of the cell, gives rise to a relatively long interval between the times of induction of beta-galactosidase and transacetylase; (ii) under conditions in which the histidine operon is derepressed, chloramphenicol causes a prolongation of the interval between the times of induction of the two enzymes, and this prolongation is reversed by adenine, methionine, and serine, compounds known to enrich the one-carbon pool of the cell; and (iii) 4-amino-5-imidazolcarboxamide ribonucleoside, a compound which may act as a drain for formyl groups, reverses the effect of the latter compounds. The finding that the interval between the times of induction of the two enzymes is shortened under conditions expected to maintain a relatively high intracellular fo rmylating capacity suggests that under certain conditions translation of the polycistronic messenger ribonucleic acid of the lactose operon may be initiated at more than one site or may proceed more rapidly from the operator end.

Acyltransferases↗
PubMed1968

Correlation between mutation type and the production of cross-reacting material in mutants of the A gene of the histidine operon in Salmonella typhimurium.

This study concerns the correlation between the type of mutation in a bacterial gene and the ability of the mutant organism to produce immunologically cross-reacting material (CRM). Ninety-five mutants of the A gene of the histidine operon in Salmonella typhimurium have been separated into three classes, by means of mutagenesis and suppression tests, according to the classification scheme devised by H. J. Whitfield, Jr., et al.: (i) missense mutants (in which there is a single amino acid substitution in the A protein); (ii) nonsense mutants (in which various portions of the carboxyl-terminal segment of the A protein are missing); and (iii) deletion and frameshift mutants. Extracts of all mutants were also examined for the presence of CRM. At least 70% of the missense mutants produced CRM. The genetic loci affected in these mutants were randomly distributed throughout the A gene. None of the nonsense, deletion, or frameshift mutants produced CRM. The absence of CRM in the nonsense mutants is in keeping with the finding that removal of the carboxyl-terminal valine residue from the A protein by carboxypeptidase A eliminates antigenicity.

Genetics, Microbial↗
PubMed1966

Correlation between location and time of expression for genes in a single operon.

When the histidine Operon in Salmonella typhimurium becomes derepressed in the presence of 4-amino-5-imidazole carboxamide ribonucleoside, derepression of the enzymes for histidine biosynthesis Occurs in a temporal sequence which corresponds with the positional sequence of the genes in the histidine Operon, approximately 20 minutes intervening between the derepression of the first and that of the last enzyme studied. In the case of the deletion mutant, hisH,B22, the interval between the derepression of the first and that of the last enzyme was reduced from 20 minutes to 10 minutes. This reduction was due exclusively to the fact that the interval between the derepressions of the two enzymes, the structural genes for which are located on either side of the deletion, was almost completely eliminated. The results support the genetic evidence for the physical absence of genetic material situated between these two genes.

Chromosome Mapping↗