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The association of tryptophan synthetase subunits from Escherichia coli and Salmonella typhimurium in homologous and heterologous combinations
Published online by Cambridge University Press: 14 April 2009
Summary
The association of α and β2 subunits of tryptophan synthetase from Escherichia coli and Salmonella typhimurium in homologous and heterologous combinations was studied by sucrose density gradient centri-fugation. Under conditions allowing for optimal association of subunits derived from the same source, subunit association in the mixture E. coli α–S. typhimurium β2 was weaker than normal while in the reciprocal combination of S. typhimurium α–E. coli β2 it was tighter than normal.
These observations suggest that a certain degree of binding between the α and β2 subunits of tryptophan synthetase could have had a selective advantage during the evolutionary divergence of the species of Entero-bacteriaceae, so that a mutation leading to the substitution of an amino acid involved in α–β2 association in one of the subunits could have been compensated by a mutation in the complementary one.
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- Copyright © Cambridge University Press 1976
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