The Effects of Mutation on the Composition and Properties of the A Protein of Escherichia coli Tryptophan Synthetase

Yanofsky, Charles; Helinski, Donald R.; Maling, Barbara D.

doi:10.1101/sqb.1961.026.01.006

Cited by 86 publications

(25 citation statements)

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“…( is likely that the growth rates of suppressed mutants will be less than that of wild type even when supplied with an excess of the end product of the pathway, in this case methionine (Yanofsky, Helinski and Maling, 1961). The suppressed metB22o and metB223 mutants grew slower on MA than wild type but there appeared to be little difference on MA + methionine.…”

Section: Isolation Of Suppressed Metb Mutantsmentioning

confidence: 96%

“…It is therefore likely that the suppressible mutants are missense mutants and the mechanism of suppression may be similar to the "mistake" hypothesis of Yanofsky, Helinski and Maling (1961) and Brody and Yanofsky (1963). The suppressors would alter the translation of the missense codon causing the incorporation of a particular amino acid into a protein at a particular frequency in place of the amino acid coded for by the missense codon, thus producing enough enzyme to permit slow growth of the mutant on unsupplemented minimal agar.…”

Section: Discussionmentioning

confidence: 99%

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Genetic analysis of suppressors of methionine mutants of Salmonella typhimurium

Childs

Smith

1967

Heredity

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Section: Isolation Of Suppressed Metb Mutantsmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Genetic analysis of suppressors of methionine mutants of Salmonella typhimurium

Childs

Smith

1967

Heredity

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“…su36+ arises in the only gene for a glycine tRNA which translates the GGA codon. Mutation leads to translation of the AGA arginine codon and there is no longer tRNA in the cell to translate GGA (Yanofsky, Helinski & Maling, 1961;Hill et al 1969;Carbon, Squires & Hill, 1970). Healthy suppressed strains are heterogenotes in which the suppressor locus is duplicated so that both the mutant and non-mutant tRNAs are synthesized.…”

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confidence: 99%

Missense Suppression in Coprinus lagopus Associated with a Chromosome Duplication

Lewis

Casselton

1975

Journal of General Microbiology

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SUMMARYAmongst some 70 recessive suppressors of a met-I mutation in Coprinus lagopus, one unstable suppressor was identified. The unstable suppressor, designated sup-6+, could be maintained on minimal medium, but was lost within 24 h on minimal medium containing more than 1.7 p.p.m. DL-methionine or 0.75 p.p.m. Lmethionine. Isolation of hyphal tips from the monokaryotic strain carrying sup-6+ yielded three types of colony: the unstable parental type, the stable met-r auxotroph and a stable prototroph which was slow-growing and inhibited by methionine in the growth medium. This stable sup-6+ type was recovered with difficulty by resolving dikaryons formed between the unstable sup-6+ strain and strains carrying the wild-type allele of the suppressor gene. From sexual crosses, neither the unstable nor stable sup-6+ type segregated, only the met-r auxotrophic revertant. The unstable sup-6' strain is thought to have an extra chromosome carrying the sup-6+ mutation. For vigorous growth the wild-type allele, sup-6-, is indispensable and would be carried on the homologous chromosome. The selective pressures on different media account for loss of the duplicated chromosomes. The results are interpreted as missense suppression by a mutant of an indispensable tRNA.

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“…While this suggests that the revertants too may be heterozygous, the situation is likely to be complex, since several reversion mechanisms, some perhaps extrachromosomal, are known to occur in bacteria. 26 Summary.-Several lines of mouse fibroblasts with a small degree of resistance to 8-azaguanine were isolated. They contained an amount of inosinic acid pyrophosphorylase activity which was intermediate between wild-type and highly resistant cells.…”

mentioning

confidence: 99%

“…"3 To investigate further the mechanism of partial resistance we have now isolated several lines of mouse fibroblasts (L cells) which show a small degree of resistance to 8-azaguanine, and have found them to contain [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] per cent of the IMP pyrophosphorylase activity of wild-type L cells. Culture methods: An inoculum of L cells was kindly supplied by Dr. L. Siminovitch in 1960, at which time the chromosome number was reported to be approximately 60.…”

mentioning

confidence: 99%

The Inosinic Acid Pyrophosphorylase Activity of Mouse Fibroblasts Partially Resistant to 8-Azaguanine

Littlefield

1963

Proc. Natl. Acad. Sci. U.S.A.

139

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Resistance to the analogue 8-azaguanine has generally been found to correlate with loss of guanylic acid-inosinic acid (IMP) pyrophosphorylase activity in several biological systems' including 3 mammalian cell lines.2-4 From 2 of these lines mutants selected for even a small degree of resistance contained very little or no pyrophosphorylase activity.2 4 From the other cell line a partially resistant mutant was also isolated in which no change in pyrophosphorylase activity occurred, as well as another mutant (resistant to 8-azaguanosine) which "displayed about onehalf of this activity."3 To investigate further the mechanism of partial resistance we have now isolated several lines of mouse fibroblasts (L cells) which show a small degree of resistance to 8-azaguanine, and have found them to contain [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] per cent of the IMP pyrophosphorylase activity of wild-type L cells. Culture methods: An inoculum of L cells was kindly supplied by Dr. L. Siminovitch in 1960, at which time the chromosome number was reported to be approximately 60. This cell line, designated "wild-type," has been maintained in suspension culture in Eagle's "spinner" medium plus 10% calf serum as previously described.6 It is free of pleuropneumonia-like organisms. Clonal lines were obtained by isolating individual colonies7 and have been stored at -70'C in medium containing 10% glycerol when not in use. 8 Determinations of drug resistance or mutant frequency were performed by inoculating an appropriate number of cells (2 X 102 to 5 X 106) from a suspension culture into replicate 60 mm

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The Effects of Mutation on the Composition and Properties of the A Protein of Escherichia coli Tryptophan Synthetase

Cited by 86 publications

References 0 publications

Genetic analysis of suppressors of methionine mutants of Salmonella typhimurium

Genetic analysis of suppressors of methionine mutants of Salmonella typhimurium

Missense Suppression in Coprinus lagopus Associated with a Chromosome Duplication

The Inosinic Acid Pyrophosphorylase Activity of Mouse Fibroblasts Partially Resistant to 8-Azaguanine

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