Open AccessEvolution of a new enzymatic function by recombination within a gene.
Author(s) -
Barry G. Hall,
Timothy J. Zuzel
Publication year - 1980
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.77.6.3529
Subject(s) - mutant , genetics , biology , beta galactosidase , gene , escherichia coli , mutation , lactose , enzyme , recombination , biochemistry
Mutations that alter the ebgA gene so that the evolved beta-galactosidase (ebg) enzyme of Escherichia coli can hydrolyze lactose fall into two classes: class I mutants use only lactose, whereas class II mutants use lactulose as well as lactose. Neither class uses galactosylarabinose effectively. In this paper we show that when both a class I and a class II mutation are present in the same ebgA gene, ebg enzyme acquires a specificity for galactosylarabinose. Although galactosylarbinose utilization can evolve as the consequence of sequential spontaneous mutations, it can also evolve via intragenic recombination in crosses between class I and class II ebgA+ mutant strains. We show that the sites for class I and class II mutations lie about 1 kilobase, or about a third of the gene, apart in ebgA. Implications of these findings with respect to the evolution of new metabolic functions discussed.