Summary
The enterobactin system for iron transport in Escherichia coli is well characterized
with the exception of the mechanism of enterobactin secretion to the extracellular
environment. Escherichia coli membrane protein P43, encoded by ybdA
in the chromosomal region of genes involved in enterobactin synthesis, shows strong
homology to the 12‐transmembrane segment major facilitator superfamily of export
pumps. A P43‐null mutation was created and siderophore nutrition assays, performed
with a panel of E. coli strains expressing one or more outer membrane receptors
for enterobactin‐related compounds, demonstrated that the P43 mutant was unable to
secrete enterobactin efficiently. Products released from the mutant strain were identified
with thin‐layer chromatography (TLC) and high‐performance liquid chromatography (HPLC),
revealing that the P43 mutant secretes little, if any, enterobactin, but elevated
levels of enterobactin breakdown products 2,3‐ dihydroxybenzoylserine (DHBS) monomer,
dimer, and trimer. These data establish that P43 is a critical component of the E.
coli enterobactin secretion machinery and provides a rationale for the designation
of the previous genetic locus ybdA as entS to reflect its relevant biological function.
A truncating mutation in canine ADAMTS17 causes PLL, a well-characterized veterinary disease, which can now be compared to a recently described rare WMS-like disease caused by truncating mutations of the human ADAMTS17 ortholog.
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