Disease relevance of tagA

• The region containing aldA and tagA comprises 13 kb of previously unidentified DNA and is part of a PAI that contains a regulator of virulence genes (ToxT) and a gene cluster encoding an essential colonization factor and the cholera toxin phage receptor (toxin-coregulated pilus; TCP) [1].
• Expression of the aldA gene was studied together with that of tagA in both V. cholerae and Escherichia coli [2].
• The Vibrio cholerae (Vc) gene (tagA) coding for the TagA lipoprotein has been isolated [3].
• Molecular and functional characterization of a ToxR-regulated lipoprotein from a clinical isolate of Aeromonas hydrophila [4].

High impact information on tagA

• We confirm that tagA strains specifically accumulate 3-methyladenine in their DNA [5].
• The function of this 898-amino-acid protein is unknown, but it exhibits 42% amino acid sequence identity and 63% similarity to a 312-amino-acid region of a ToxR-regulated lipoprotein of Vibrio cholerae [6].
• Sequencing of tagA revealed the presence of an open reading frame (ORF) of 568 amino acids with a characteristic signal peptidase II cleavage site at the N terminus [3].
• While the portion of the tagA gene product examined presented no extensive similarity to any known protein, the amino acid sequence deduced from an open reading frame (designated aldA) located upstream from and in opposite orientation to tagA was highly similar to the sequences of eukaryotic aldehyde dehydrogenases [2].
• The latter group includes virulence genes involved in the biogenesis of the TCP pilus, the accessory colonization factor, and such ToxR-activated genes as tagA, mutations in which cause no detectable virulence defect in the suckling mouse model [2].

Biological context of tagA

• Each hybrid plasmid directed the synthesis of 21-kDa m3ADG in E. coli tagA- ada-, which were not inhibited by 4 mM m3A [7].
• In all cases, the tagA mutation, which inactivates the constitutive and specific 3-alkyladenine-DNA glycosylase I (TagI), sensitizes the strain to the SOS response [8].

References