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1nqg

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[[Image:1nqg.gif|left|200px]]
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{{STRUCTURE_1nqg| PDB=1nqg | SCENE= }}
{{STRUCTURE_1nqg| PDB=1nqg | SCENE= }}
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'''OUTER MEMBRANE COBALAMIN TRANSPORTER (BTUB) FROM E. COLI, WITH BOUND CALCIUM'''
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===OUTER MEMBRANE COBALAMIN TRANSPORTER (BTUB) FROM E. COLI, WITH BOUND CALCIUM===
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==Overview==
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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.
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(as it appears on PubMed at http://www.pubmed.gov), where 12652322 is the PubMed ID number.
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{{ABSTRACT_PUBMED_12652322}}
==About this Structure==
==About this Structure==
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[[Category: Membrane transport]]
[[Category: Membrane transport]]
[[Category: Vitamin b12]]
[[Category: Vitamin b12]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 02:51:33 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 07:41:34 2008''

Revision as of 04:41, 28 July 2008

Image:1nqg.png

Template:STRUCTURE 1nqg

OUTER MEMBRANE COBALAMIN TRANSPORTER (BTUB) FROM E. COLI, WITH BOUND CALCIUM

Template:ABSTRACT PUBMED 12652322

About this Structure

1NQG is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

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 Mon Jul 28 07:41:34 2008

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