1nqe: Difference between revisions

Revision as of 15:08, 21 February 2008

OUTER MEMBRANE COBALAMIN TRANSPORTER (BTUB) FROM E. COLI

OverviewOverview

The outer membranes of Gram-negative bacteria possess transport proteins essential for uptake of scarce nutrients. In TonB-dependent transporters, a conserved sequence of seven residues, the Ton box, faces the periplasm and interacts with the inner membrane TonB protein to energize an active transport cycle. A critical mechanistic step is the structural change in the Ton box of the transporter upon substrate binding; this essential transmembrane signaling event increases the affinity of the transporter for TonB and enables active transport to proceed. We have solved crystal structures of BtuB, the outer membrane cobalamin transporter from Escherichia coli, in the absence and presence of cyanocobalamin (vitamin B(12)). In these structures, the Ton box is ordered and undergoes a conformational change in the presence of bound substrate. Calcium has been implicated as a necessary factor for the high-affinity binding (K(d) approximately 0.3 nM) of cyanocobalamin to BtuB. We observe two bound calcium ions that order three extracellular loops of BtuB, thus providing a direct (and unusual) structural role for calcium.

About this StructureAbout this Structure

1NQE is a Single protein structure of sequence from Escherichia coli with and as ligands. Full crystallographic information is available from OCA.

ReferenceReference

Substrate-induced transmembrane signaling in the cobalamin transporter BtuB., Chimento DP, Mohanty AK, Kadner RJ, Wiener MC, Nat Struct Biol. 2003 May;10(5):394-401. PMID:12652322

Page seeded by OCA on Thu Feb 21 14:08:53 2008

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OCA

@@ Line 1: / Line 1: @@
-[[Image:1nqe.gif|left|200px]]<br /><applet load="1nqe" size="450" color="white" frame="true" align="right" spinBox="true"
+[[Image:1nqe.gif|left|200px]]<br /><applet load="1nqe" size="350" color="white" frame="true" align="right" spinBox="true"
 caption="1nqe, resolution 2.00&Aring;" />
 '''OUTER MEMBRANE COBALAMIN TRANSPORTER (BTUB) FROM E. COLI'''<br />
 ==Overview==
-The outer membranes of Gram-negative bacteria possess transport proteins, essential for uptake of scarce nutrients. In TonB-dependent transporters, a conserved sequence of seven residues, the Ton box, faces the periplasm, and interacts with the inner membrane TonB protein to energize an active, transport cycle. A critical mechanistic step is the structural change in, the Ton box of the transporter upon substrate binding; this essential, transmembrane signaling event increases the affinity of the transporter, for TonB and enables active transport to proceed. We have solved crystal, structures of BtuB, the outer membrane cobalamin transporter from, Escherichia coli, in the absence and presence of cyanocobalamin (vitamin, B(12)). In these structures, the Ton box is ordered and undergoes a, conformational change in the presence of bound substrate. Calcium has been, implicated as a necessary factor for the high-affinity binding (K(d), approximately 0.3 nM) of cyanocobalamin to BtuB. We observe two bound, calcium ions that order three extracellular loops of BtuB, thus providing, a direct (and unusual) structural role for calcium.
+The outer membranes of Gram-negative bacteria possess transport proteins essential for uptake of scarce nutrients. In TonB-dependent transporters, a conserved sequence of seven residues, the Ton box, faces the periplasm and interacts with the inner membrane TonB protein to energize an active transport cycle. A critical mechanistic step is the structural change in the Ton box of the transporter upon substrate binding; this essential transmembrane signaling event increases the affinity of the transporter for TonB and enables active transport to proceed. We have solved crystal structures of BtuB, the outer membrane cobalamin transporter from Escherichia coli, in the absence and presence of cyanocobalamin (vitamin B(12)). In these structures, the Ton box is ordered and undergoes a conformational change in the presence of bound substrate. Calcium has been implicated as a necessary factor for the high-affinity binding (K(d) approximately 0.3 nM) of cyanocobalamin to BtuB. We observe two bound calcium ions that order three extracellular loops of BtuB, thus providing a direct (and unusual) structural role for calcium.
 ==About this Structure==
-NQE is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with MG and C8E as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1NQE OCA].
+NQE is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=MG:'>MG</scene> and <scene name='pdbligand=C8E:'>C8E</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NQE OCA].
 ==Reference==
@@ Line 13: / Line 13: @@
 [[Category: Escherichia coli]]
 [[Category: Single protein]]
-[[Category: Chimento, D.P.]]
+[[Category: Chimento, D P.]]
-[[Category: Kadner, R.J.]]
+[[Category: Kadner, R J.]]
-[[Category: Mohanty, A.K.]]
+[[Category: Mohanty, A K.]]
-[[Category: Wiener, M.C.]]
+[[Category: Wiener, M C.]]
 [[Category: C8E]]
 [[Category: MG]]
@@ Line 24: / Line 24: @@
 [[Category: vitamin b12]]
-''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Tue Nov 20 22:29:01 2007''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:08:53 2008''