Prephenate dehydratase from the aphid endosymbiont (Buchnera) displays changes in the regulatory domain that suggest its desensitization to inhibition by phenylalanine.
Buchnera aphidicola, the prokaryotic endosymbiont of aphids, complements dietary deficiencies with the synthesis and provision of several essential amino acids. We have cloned and sequenced a region of the genome of B. aphidicola isolated from Acyrthosiphon pisum which includes the two-domain aroQ/pheA gene. This gene encodes the bifunctional chorismate mutase-prephenate dehydratase protein, which plays a central role in L-phenylalanine biosynthesis. Two changes involved in the overproduction of this amino acid have been detected. First, the absence of an attenuator region suggests a constitutive expression of this gene. Second, the regulatory domain of the Buchnera prephenate dehydratase shows changes in the ESRP sequence, which is involved in the allosteric binding of phenylalanine and is strongly conserved in prephenate dehydratase proteins from practically all known organisms. These changes suggest the desensitization of the enzyme to inhibition by phenylalanine and would permit the bacterial endosymbiont to overproduce phenylalanine.
Jiménez
N
N
Institut Cavanilles de Biodiversitat i Biologia Evolutiva and Departament de Genètica, Universitat de València, 46071 València, Spain.
González-Candelas
F
F
Silva
F J
FJ
D000595:Amino Acid Sequence; D000818:Animals; D001042:Aphids / Q000382:microbiology*; D001483:Base Sequence; D001665:Binding Sites; D020635:Buchnera / Q000201:enzymology* / Q000235:genetics; D002826:Chorismate Mutase / Q000235:genetics*; D004269:DNA, Bacterial; D004791:Enzyme Inhibitors; D004926:Escherichia coli / Q000235:genetics; D016680:Genome, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000378:metabolism*; D011302:Prephenate Dehydratase / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013559:Symbiosis
D004269:DNA, Bacterial; D004791:Enzyme Inhibitors; D010649:Phenylalanine; D011302:Prephenate Dehydratase; D002826:Chorismate Mutase