Abstract
A cell-free system allowing for synthesis of β-galactosidase enzymatic activity has been developed. This system requires DNA containing the β-galactosidase gene, a cell-free extract of Escherichia coli bacteria, and the low-molecular-weight components necessary for transcription of the DNA and translation of the resulting messenger RNA. Such a system is useful for studying enzyme synthesis, as well as its regulation. The gene for β-galactosidase is part of the lac operon whose expression is under the control of the lac repressor. In whole cells the lac repressor inhibits almost all of the gene expression for β-galactosidase. In the cell-free system, we had previously been able to repress about half the gene expression. Adding cyclic adenosine 3′5′-monophosphate to the cell-free system improved the yield of β-galactosidase enzymatic activity by 8 to 30 times and the efficiency of repression from 50 to 95 per cent.
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Selected References
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