Disease relevance of C06769

• We report the crystal structure of the free-standing NRPS condensation (C) domain VibH, which catalyzes amide bond formation in the synthesis of vibriobactin, a Vibrio cholerae siderophore [1].
• The six-domain, 270 kDa nonribosomal peptide synthetase (NRPS) VibF, a component of vibriobactin synthetase, has been heterologously expressed in Escherichia coli and purified [2].
• Finally, vibriobactin is also shown to be active with a human Burkitt lymphoma cell line (Daudi) [3].

High impact information on C06769

• In the mutant, a plasmid containing these genes permitted transport via the known V. cholerae high-affinity iron transport systems, including uptake of haem, vibriobactin and ferrichrome [4].
• Catalytically inactive condensation domain C1 is responsible for the dimerization of the VibF subunit of vibriobactin synthetase [5].
• The Vibrio cholerae siderophore vibriobactin is biosynthesized from three molecules of 2,3-dihydroxybenzoate (DHB), two molecules of L-threonine, and one of norspermidine [6].
• This diacylated product undergoes a second aryl oxazoline acylation on its remaining secondary amine, also catalyzed by VibF, to yield vibriobactin [2].
• The N-terminal amino acid sequence of a 72-kDa iron-regulated outer membrane protein purified from a V. vulnificus fur mutant had 53% homology with the first 15 amino acids of the mature protein of the Vibrio cholerae vibriobactin receptor, ViuA [7].

Chemical compound and disease context of C06769

• Vibrio cholerae uses the catechol siderophore vibriobactin for iron transport under iron-limiting conditions [8].
• The ViuPDGC system transports both vibriobactin and enterobactin in Escherichia coli [8].

Biological context of C06769

• We have identified genes for vibriobactin transport and mapped them within the vibriobactin biosynthetic gene cluster [8].
• Chromosomal DNA downstream of the Vibrio cholerae ferric vibriobactin receptor gene, viuA, was cloned and sequenced, revealing an 813-bp open reading frame encoding a deduced protein of 271 amino acids [9].
• DNA sequences encoding the gene into which TnphoA had inserted, designated viuA (vibriobactin uptake), restored the wild-type phenotype to the mutant; the complemented mutant expressed the 74-kDa outer membrane protein under iron-limiting conditions and possessed normal vibriobactin binding and uptake [10].
• The microbial iron chelator vibriobactin, N-[3-(2,3-dihydroxybenzamido)propyl]-1,3-bis[2-(2, 3-dihydroxyphenyl)-trans-5-methyl-2-oxazoline-4-carboxamido]-propane, is shown to inhibit the growth of L1210 cells in culture, with an IC50 value of 2 microM [3].
• Furthermore, after exposure of L1210 cells to vibriobactin (10 microM) for 5 hrs followed by removal of the drug, cells display different doubling times relative to untreated controls, with lower bromodeoxyuridine (BrdUrd) incorporation and no apparent cell death as shown by a 51Cr release assay [3].

Gene context of C06769

• Vibrio cholerae has multiple iron acquisition systems, including TonB-dependent transport of heme and of the catechol siderophore vibriobactin [11].
• Unexpectedly, hydropathicity analysis of ViuB did not reveal a signal sequence or transmembrane domain, suggesting that ViuB is not a periplasmic or membrane protein but may be a cytoplasmic protein involved in ferric vibriobactin uptake and processing, perhaps analogous to the Escherichia coli protein Fes [9].

Analytical, diagnostic and therapeutic context of C06769

• The isolated domain was well-folded when compared by circular dichroism to the vibriobactin NRPS VibH, a naturally free-standing C domain [12].
• Dimeric structure of the six-domain VibF subunit of vibriobactin synthetase: mutant domain activity regain and ultracentrifugation studies [13].

References