2o6a
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Crystal structure of the Haemophilus influenzae E57A mutant FbpA
OverviewOverview
The periplasmic iron binding protein, FbpA, performs an essential role in, iron acquisition from transferrin in Haemophilus influenzae. Site-directed, mutants in the metal binding amino acids of FbpA were prepared to, determine their relative contribution to iron-binding and transport., Structural studies demonstrated that the mutant proteins crystallized in, an open conformation with the iron atom associated with the C-terminal, domain. The iron-binding properties of the mutant proteins were assessed, by several assays, including a novel competitive iron-binding assay. The, relative ability of the proteins to compete for iron was pH dependent, with a rank order at pH 6.5 of WT, Q58L, H9Q > H9A, E57A > Y195A, Y196A., The genes encoding the mutant FbpA proteins were introduced into H., influenzae and the resulting strains varied in the level of ferric citrate, required to support growth on iron-limited medium, inferring a rank order, for metal binding affinities under physiological conditions comparable to, the competitive binding assay at pH 6.5 (WT = Q58L > H9Q > H9A, E57A >, Y195A, Y196A). Growth dependant upon human transferrin was only obtained, with cells expressing wild-type, Q58L or H9Q FbpAs, proteins with, stability constants derived from the competition assay greater than or, equal to 2.0 x 10 18 M -1. These results suggest that a relatively high, affinity of iron binding by FbpA is required for removal of iron from, transferrin and its transport across the outer membrane.
About this StructureAbout this Structure
2O6A is a Single protein structure of sequence from Haemophilus influenzae with and as ligands. Full crystallographic information is available from OCA.
ReferenceReference
High affinity binding by the periplasmic iron binding protein from Haemophilus influenzae is required for acquiring iron from transferrin., Khan AG, Shouldice SR, Kirby SD, Yu RH, Tari LW, Schryvers AB, Biochem J. 2007 Feb 21;. PMID:17313366
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