1d9v: Difference between revisions

Revision as of 13:14, 21 February 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 with as ligand. 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 Thu Feb 21 12:14:32 2008

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-[[Image:1d9v.jpg|left|200px]]<br /><applet load="1d9v" size="450" color="white" frame="true" align="right" spinBox="true"
+[[Image:1d9v.jpg|left|200px]]<br /><applet load="1d9v" size="350" color="white" frame="true" align="right" spinBox="true"
 caption="1d9v, resolution 1.75&Aring;" />
 '''HAEMOPHILUS INFLUENZAE FERRIC-BINDING PROTEIN APO FORM'''<br />
 ==Overview==
-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.
+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 Structure==
-D9V is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Haemophilus_influenzae Haemophilus influenzae] with PO4 as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1D9V OCA].
+D9V is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Haemophilus_influenzae Haemophilus influenzae] with <scene name='pdbligand=PO4:'>PO4</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1D9V OCA].
 ==Reference==
@@ Line 13: / Line 13: @@
 [[Category: Haemophilus influenzae]]
 [[Category: Single protein]]
-[[Category: Bruns, C.M.]]
+[[Category: Bruns, C M.]]
-[[Category: McRee, D.E.]]
+[[Category: McRee, D E.]]
-[[Category: Williams, P.A.]]
+[[Category: Williams, P A.]]
 [[Category: PO4]]
 [[Category: abc cassette receptor protein]]
@@ Line 24: / Line 24: @@
 [[Category: periplasmic protein]]
-''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Tue Nov 20 13:06:46 2007''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:14:32 2008''