Mutational analysis of the catalytic and feedback sites of the tryptophan-sensitive 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase of Escherichia coli.
AUTOR(ES)
Ray, J M
RESUMO
The nucleotide sequence of aroH, the structural gene for the tryptophan-sensitive 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase [DAHPS(Trp)], is presented, and the deduced amino acid sequence of AroH is compared with that of the tyrosine-sensitive (AroF) and phenylalanine-sensitive (AroG) DAHPS isoenzymes. The high degree of sequence similarity among the three isoenzymes strongly indicates that they have a common evolutionary origin. In vitro chemical mutagenesis of the cloned aroH gene was used to identify residues and regions of the polypeptide essential for catalytic activity and for tryptophan feedback regulation. Missense mutations leading either to loss of catalytic activity or to feedback resistance were found interspersed throughout the polypeptide, suggesting overlapping catalytic and regulatory sites in DAHPS(Trp). We conclude that the specificity of feedback regulation of the isoenzymes was probably acquired by the duplication and divergent evolution of an ancestral gene, rather than by domain recruitment.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=211643Documentos Relacionados
- Purification and properties of tryptophan-sensitive 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Escherichia coli.
- Mutational analysis of the feedback sites of phenylalanine-sensitive 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase of Escherichia coli.
- Evolution of 3-deoxy-d-arabino-heptulosonate-7-phosphate synthase-encoding genes in the yeast Saccharomyces cerevisiae
- Is the first enzyme of the shikimate pathway, 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (tyrosine sensitive), a copper metalloenzyme?
- Characterization of a recombinant type II 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Helicobacter pylori