The synthesis of β-galactosidase inEscherichia coli in the presence of Methionine analogues
The effect of methionine analogues, selenomethionine and selenoethionine, on the synthesis of β-galactosidase inEscherichia coli was investigated. It was found that the incorporation of selenomethionine into β-galactosidase results in the formation of a protein exhibiting normal enzyme activity and immunologically cross-reacting with the antiserum against normal β-galactosidase. However, the selenomethionine enzyme was found to be more susceptible to heat, urea and trypsin. On the other hand, an immunologically cross-reacting protein without the enzyme activity was synthesized in the presence of selenoethionine. The results obtained seem to support the idea that the presence of methionine methyl groups is essential for the activity of β-galactosidase, whereas methionine sulphur can be replaced without changing the enzyme activity.
KeywordsMethionine Selenomethionine Ethionine Immunological Test Bacterial Extract
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