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. 1974 Mar;117(3):1231–1239. doi: 10.1128/jb.117.3.1231-1239.1974

Inhibition of lacZ Gene Translation Initiation in trp-lac Fusion Strains

William S Reznikoff 1, Corinne A Michels 1,1, Terrance G Cooper 1,2, Allen E Silverstone 1, Boris Magasanik 1
PMCID: PMC246606  PMID: 4591949

Abstract

Different levels of β-galactosidase are found in various trp-lac fusion strains. These levels of β-galactosidase fall within a 60-fold range. The amount of thiogalactoside transacetylase activity detected in these same strains only varies 10-fold and is found in amounts greater than those predicted from the β-galactosidase levels. The observation that the β-galactosidase and thiogalactoside transacetylase levels are not directly proportional, that the lacZ messenger ribonucleic acid (mRNA) levels are not proportional to the β-galactosidase activity, that, at least for the one fusion strain tested, the SuA polarity suppressor does not affect the β-galactosidase level, and that, in all but one strain, the β-galactosidase activity appears to reside in normal β-galactosidase molecules suggests that the disproportionately low production of β-galactosidase is due to a decrease in the frequency of translation initiation of lacZ mRNA in these strains. Several mechanisms are proposed to explain this decrease. Some possible bases for the disproportional production of β-galactosidase and thiogalactoside transacetylase are also described. The preferred explanation for these disproportional enzyme levels is that only a fraction of the full complement of ribosomes need initiate translation at lacZ for the functional synthesis of lac mRNA to occur and that once the lac ribonucleic acid is made a full complement of ribosomes can bind at internal translation initiation sites at Y and A.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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