Partial Reversion in Yeast: Genetic Evidence for a New Type of Bifunctional Protein

Dorfman, Ben-Zion; Goldfinger, B.; Berger, Marc; Goldstein, Solomon

doi:10.1126/science.168.3938.1482

Cited by 18 publications

(2 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The idea that the mutations in the dihydrofolate reductase gene might alter regulation at the transcriptional level is difficult to envision unless one presumes a regulatory role for this enzyme protein. The existence of this type of bifunctional protein was suggested by the work of Dorfman et al (4). Finally, an effect of a structural gene mutation similar to those described here was observed in the case of the overproduction of two human enzymes (20,21).…”

Section: Resultssupporting

confidence: 78%

High Dihydrofolate Reductase Levels in Diplococcus pneumoniae After Mutation in the Structural Gene: Biochemical and Immunological Evidence for Increased Synthesis

Sirotnak

1971

J Bacteriol

View full text Add to dashboard Cite

A unique class of missense mutations in the dihydrofolate reductase structural gene of Diplococcus pneumoniae determines marked increases in the corresponding enzyme activity. Immunological evidence, based on precipitating and neutralizing antibody reactions, is presented in support of previously derived findings which attribute this increase in activity to an increase in the amount of enzyme protein.Biochemical evidence was obtained which shows that the increased amounts of dihydrofolate reductase protein in the mutants not owing to a decrease in degradation, reducing turnover, or to an increase in stability, and, therefore, probably related to an increase in the rate of synthesis of new protein. The manner in which a missense alteration of a structural gene might quantitatively alter the expression of that gene is discussed.Immunoassay. Antibody against dihydrofolate reductase was prepared in a female albino rabbit by two injections, 10 days apart, of 0.5 mg of purified dihydrofolate reductase protein in I ml of 0.02 M 318 on July 16, 2020 by guest http://jb.asm.org/ Downloaded from VOL. 106, 1971 DIHYDROFOLATE REDUCTASE LEVELS IN D. PNEUMONIAE 320 SIROTNAK on July 16, 2020 by guest

show abstract

Section: Resultssupporting

confidence: 78%

High Dihydrofolate Reductase Levels in Diplococcus pneumoniae After Mutation in the Structural Gene: Biochemical and Immunological Evidence for Increased Synthesis

Sirotnak

1971

J Bacteriol

View full text Add to dashboard Cite

show abstract

“…Starting strains included M41, I-17A, and E1813, previously described (3); Es-3, a, trp5, lys2, ural, ade2, and Es-5, a, trp5, lys2, ural, ade2, obtained from M. Esposito as I-17B and I-17D, respectively; E831, a, trp5, lys2, ural, adel derived from Esposito's 1-17A; and A1205D, a, ural, ade2. Symbols, media, and culture conditions were previously described (3,4). Minimal medium (MM), supplemented with 25 ug of histidine per ml (MH) was used to test growth of diploids in the absence of adenine when markers other than adel2 were all heterozygous; another replicate, with adenine sulfate at 200 ug/ml (MHAD), served as a positive control.…”

mentioning

confidence: 99%

Allelic Variability in Comparative Complementation Confirming that the adel2 -Specified Protein of Yeast is Bifunctional

Dorfman

1971

J Bacteriol

Self Cite

View full text Add to dashboard Cite

Mutants at the adel2 locus of Saccharomyces cerevisiae are deficient in adenylosuccinate synthetase and are also responsible for constitutive purine biosynthetic activity. Ninety-six alleles were tested for restoration of each of these functions by allelic complementation and the results from the two types of test of every allele pair in the two matrices were compared with each other. Either the reactions were consistent, both complementing or noncomplementing, or inconsistent, with either enzymatic or regulatory function restored. The frequency and distribution of inconsistent behavior accords with the expectation that the adel2 locus specifies a bifunctional protein serving independent roles in enzymatic activity and in regulation of pathway activity. In a parallel experiment and analysis the addition of 1.0 m KCl increases the overall frequency of positive complementation, but skews the distribution of inconsistency sharply toward restoration of the regulatory function.

show abstract

Increased PRPP synthetase activity in cultured rat hepatoma cells containing mutations in the hypoxanthine‐guanine phosphoribosyltransferase gene

Graf

McRoberts

Harrison

et al. 1976

Journal Cellular Physiology

View full text Add to dashboard Cite

Nine independently derived clones of mutagenized rat hepatoma cells selected for resistance to 6-mercaptopurine (6-MP) or 6-thioguanine (6-ThioG) have been isolated. Each has severely reduced catalytic activity of hypoxanthine-guanine phosphoribosyltransferase (HPRT) and seven of them possess significantly increased activities of phosphoribosylpyrophosphate (PRPP) synthetase. The degrees of elevations of PRPP synthetase activities do not correlate with the degrees of deficiencies of HPRT activities. The cells from one of these clones, 1020/12, posses 40% of the normal HPRT catalytic activity and overproduce purines. We have extensively examined the cells from this clone. Immunotration studies of 1020/12 cells indicate that there is a mutation in the structural gene for HPRT. Although they possess increased specific catalytic activities of the enzyme. PRPP synthetase, the catalytic parameters, heat stability, and isoelectric pH of PRPP synthetase from 1020/12 cells are indistinguishable from those of the enzyme from wild-type cells. The cause of purine overproduction by 1020/12 cells appears to be the elevated PRPP synthetase activity, rather than a PRPP "sparing" effect stemming from reduced HPRT activity. Support for this idea is provided by the observation that the complete loss of HPRT activity in a clone derived from 1020/12 cells does not further enhance the levels of PRPP synthetase or purine overproduction. We propose that the elevated levels of PRPP synthetase activity in these HPRT deficient cells result from a mutational event in the structural gene for HPRT, and that this causes the disruption of a previously undescribed regulatory function of this gene on the expression of the PRPP synthetase gene.

show abstract

Partial Reversion in Yeast: Genetic Evidence for a New Type of Bifunctional Protein

Cited by 18 publications

References 11 publications

High Dihydrofolate Reductase Levels in Diplococcus pneumoniae After Mutation in the Structural Gene: Biochemical and Immunological Evidence for Increased Synthesis

High Dihydrofolate Reductase Levels in Diplococcus pneumoniae After Mutation in the Structural Gene: Biochemical and Immunological Evidence for Increased Synthesis

Allelic Variability in Comparative Complementation Confirming that the adel2 -Specified Protein of Yeast is Bifunctional

Increased PRPP synthetase activity in cultured rat hepatoma cells containing mutations in the hypoxanthine‐guanine phosphoribosyltransferase gene

Contact Info

Product

Resources

About