| Literature References | 1. PAYNE, S.M.
Detection, isolation, and characterisation of siderophores.
METHODS ENZYMOL. 235 329-344 (1994).
2. NAHLIK, M.S., BRICKMAN, T.J., OZENBERGER, B.A. AND MCINTOSH, M.A.
Nucleotide sequence and transcriptional organisation of the Escherichia
coli enterobactin biosynthesis cistrons entB and entA.
J.BACTERIOL. 171 784-790 (1989).
3. WYCKOFF, E.E., STOEBNER, J.A., REED, K.E. AND PAYNE, S.M.
Cloning of a Vibrio cholera vibriobactin gene cluster: identification of
genes required for early steps in siderophore synthesis.
J.BACTERIOL. 179 7055-7062 (1997).
4. LIU, J., DUNCAN, K. AND WALSH, C.T.
Nucleotide sequence of a cluster of Escherichia coli enterobactin
biosynthesis genes: identification of entA and purification of its product
2,3-dihydro-2,3-dihydroxybenzoate dehydrogenase.
J.BACTERIOL. 171 791-798 (1989).
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| Documentation | Iron is essential for growth in both bacteria and mammals. Controlling the
amount of free iron in solution is often used as a tactic by hosts to limit
invasion of pathogenic microbes; binding iron tightly within protein
molecules can accomplish this. Such iron-protein complexes include haem in
blood, lactoferrin in tears/saliva and transferrin in blood plasma. Some
bacteria express surface receptors to capture eukaryotic iron-binding
compounds, while others have evolved siderophores to scavenge iron from
iron-binding host proteins [1].
The absence of free iron molecules in the surrounding environment triggers
transcription of gene clusters that encode both siderophore-synthesis
enzymes, and receptors that recognise iron-bound siderophores [2]. Classic
examples are the enterobactin/enterochelin clusters found in Escherichia
coli and Salmonella spp., although similar moieties in other pathogens have
been identified. The enzymic machinery that produces vibrionectin in Vibrio
cholera is such a homologue [3].
EntD forms part of the enterobactin-synthetase enzyme complex. It is
involved in the final stage of enterobactin biosynthesis, converting
2,3-dihydroxybenzoic acid (DHBA) and L-serine to enterobactin. Deletion
studies involving EntD- mutants have shown that it is essential for
virulence [4].
ENTSNTHTASED is a 3-element fingerprint that provides a signature for
enterobactin synthetase component D proteins. The fingerprint was derived
from an initial alignment of 3 sequences: the motifs were drawn from
conserved regions spanning the full alignment length (~160 amino acids).
Two iterations on SPTR37_10f were required to reach convergence, at
which point a true set comprising 10 sequences was identified.
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