1d9v: Difference between revisions
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{{STRUCTURE_1d9v| PDB=1d9v | SCENE= }} | |||
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'''HAEMOPHILUS INFLUENZAE FERRIC-BINDING PROTEIN APO FORM''' | '''HAEMOPHILUS INFLUENZAE FERRIC-BINDING PROTEIN APO FORM''' | ||
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[[Category: McRee, D E.]] | [[Category: McRee, D E.]] | ||
[[Category: Williams, P A.]] | [[Category: Williams, P A.]] | ||
[[Category: | [[Category: Abc cassette receptor protein]] | ||
[[Category: | [[Category: Apo form]] | ||
[[Category: | [[Category: Binding protein]] | ||
[[Category: | [[Category: Ferric]] | ||
[[Category: | [[Category: Iron]] | ||
[[Category: | [[Category: Periplasmic protein]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 13:36:43 2008'' | |||
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Revision as of 13:36, 2 May 2008
HAEMOPHILUS INFLUENZAE FERRIC-BINDING PROTEIN APO FORM
OverviewOverview
The crystal structure of the iron-free (apo) form of the Haemophilus influenzae Fe(3+)-binding protein (hFbp) has been determined to 1.75 A resolution. Information from this structure complements that derived from the holo structure with respect to the delineation of the process of iron binding and release. A 21 degrees rotation separates the two structural domains when the apo form is compared with the holo conformer, indicating that upon release of iron, the protein undergoes a change in conformation by bending about the central beta-sheet hinge. A surprising finding in the apo-hFbp structure was that the ternary binding site anion, observed in the crystals as phosphate, remained bound. In solution, apo-hFbp bound phosphate with an affinity K(d) of 2.3 x 10(-3) M. The presence of this ternary binding site anion appears to arrange the C-terminal iron-binding residues conducive to complementary binding to Fe(3+), while residues in the N-terminal binding domain must undergo induced fit to accommodate the Fe(3+) ligand. These observations suggest a binding process, the first step of which is the binding of a synergistic anion such as phosphate to the C-terminal domain. Next, iron binds to the preordered half-site on the C-terminal domain. Finally, the presence of iron organizes the N-terminal half-site and closes the interdomain hinge. The use of the synergistic anion and this iron binding process results in an extremely high affinity of the Fe(3+)-binding proteins for Fe(3+) (nFbp K'(eff) = 2.4 x 10(18) M(-1)). This high-affinity ligand binding process is unique among the family of bacterial periplasmic binding proteins and has interesting implications in the mechanism of iron removal from the Fe(3+)-binding proteins during FbpABC-mediated iron transport across the cytoplasmic membrane.
About this StructureAbout this Structure
1D9V is a Single protein structure of sequence from Haemophilus influenzae. Full crystallographic information is available from OCA.
ReferenceReference
Crystallographic and biochemical analyses of the metal-free Haemophilus influenzae Fe3+-binding protein., Bruns CM, Anderson DS, Vaughan KG, Williams PA, Nowalk AJ, McRee DE, Mietzner TA, Biochemistry. 2001 Dec 25;40(51):15631-7. PMID:11747438 Page seeded by OCA on Fri May 2 13:36:43 2008