Evolution of a new enzymatic function by recombination within a gene.
AUTOR(ES)
Hall, B G
RESUMO
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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=349650Documentos Relacionados
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