Temperature-sensitive revertants

Chung, Shiau-Ta; Greenberg, Gordon R.

doi:10.1016/0006-291x(71)90166-5

Cited by 7 publications

(1 citation statement)

References 12 publications

(7 reference statements)

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“…Although an enrichment method for thermosensitive aminoacyl-tRNA synthetase mutants has been devised (21), this method yields a great preponderance of only a few types (24), and the thermosensitive tyrS mutants described in this paper are the first so far reported. The concept of selecting thermosensitive mutants by reversion is a relatively old one (25) and has recently been revived as a general procedure (9).…”

Section: Discussionmentioning

confidence: 99%

Regulation of the Tyrosine Biosynthetic Enzymes in Salmonella typhimurium : Analysis of the Involvement of Tyrosyl-Transfer Ribonucleic Acid and Tyrosyl-Transfer Ribonucleic Acid Synthetase

1972

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Mutants of Salmonella typhimurium were isolated that require tyrosine for growth because of an altered tyrosyl-transfer ribonucleic acid (tRNA) synthetase. Extracts of one strain (JK10) contain a labile enzyme with decreased ability to transfer tyrosine to tRNA Tyr and a higher K m for tyrosine than the wild-type enzyme. Strain JK10 maintains repressed levels of the tyrosine biosynthetic enzymes when the growth rate is restricted due to limitation of charged tRNA Tyr . Several second-site revertants of strain JK10 exhibit temperature-sensitive growth due to partially repaired, heat-labile tyrosyl-tRNA synthetase. The tyrosine biosynthetic enzymes are not derepressed in thermosensitive strains grown at the restrictive temperature. A class of tyrosine regulatory mutants, designated tyrR , contains normal levels of tyrosyl-tRNA synthetase and tRNA Tyr . These results suggest that charging of tRNA Tyr is not necessary for repression. This conclusion is substantiated by the finding that 4-aminophenylalanine, a tyrosine analogue which causes repression of the tyrosine biosynthetic enzymes, is not attached to tRNA Tyr in vivo, nor does it inhibit the attachment reaction in vitro. A combined regulatory effect due to the simultaneous presence of tyrS and tyrR mutations in the same strain was detected. The possibility of direct participation of tyrosyl-tRNA synthetase in tyrosine regulation is discussed.

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Section: Discussionmentioning

confidence: 99%

Regulation of the Tyrosine Biosynthetic Enzymes in Salmonella typhimurium : Analysis of the Involvement of Tyrosyl-Transfer Ribonucleic Acid and Tyrosyl-Transfer Ribonucleic Acid Synthetase

1972

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Regulation of maltose fermentation in Saccharomyces carlsbergensis

Berge¹,

Zoutewelle²,

Poll³

1973

Molec. Gen. Genet.

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Isolation and characterization of yeast mutants auxotrophic for 2′-deoxythymidine 5′-monophosphate

Little

Haynes

1979

Molec. Gen. Genet.

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Mutant strains of Saccharomyces cerevisiae auxotrophic for deoxythymidine monophosphate (dTMP) were isolated and characterized. Two distinct classes of auxotrophs were obtained. One class had a simple requirement for dTMP and was analogous to thymine-requiring bacteria. The second class required dTMP, adenine, histidine and methionine and this complex nutritional phenotype was due to defects in folate metabolism. The dTMP-dependent growth of respiratory-competent grande auxotrophs was found to be markedly affected by media composition and carbon source. In the absence of dTMP thymineless death occurred in both mutant classes.

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Temperature-sensitive revertants

Abstract: About 50% of a series of non-temperature-sensitive, spontaneously revertable auxotrophs of Escheriohia coti showed temperaturesensitive revertants when the selection was at 25O rather than at 37'. This procedure provides a simple device to select temperature-sensitive mutants.

Cited by 7 publications

References 12 publications

Regulation of the Tyrosine Biosynthetic Enzymes in Salmonella typhimurium : Analysis of the Involvement of Tyrosyl-Transfer Ribonucleic Acid and Tyrosyl-Transfer Ribonucleic Acid Synthetase

Regulation of the Tyrosine Biosynthetic Enzymes in Salmonella typhimurium : Analysis of the Involvement of Tyrosyl-Transfer Ribonucleic Acid and Tyrosyl-Transfer Ribonucleic Acid Synthetase

Regulation of maltose fermentation in Saccharomyces carlsbergensis

Isolation and characterization of yeast mutants auxotrophic for 2′-deoxythymidine 5′-monophosphate

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