1NQG

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

1NQG の概要

• エントリーDOI: 10.2210/pdb1nqg/pdb
• 関連するPDBエントリー: 1NQE 1NQF 1NQH
• 分子名称: vitamin b12 receptor, CALCIUM ION, (HYDROXYETHYLOXY)TRI(ETHYLOXY)OCTANE (3 entities in total)
• 機能のキーワード: beta barrel, cobalamin, vitamin b12, membrane transport, calcium binding, transport protein
• 由来する生物種: Escherichia coli
• 細胞内の位置: Cell outer membrane; Multi-pass membrane protein: P06129
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 68385.12

構造登録者

Chimento, D.P.,Mohanty, A.K.,Kadner, R.J.,Wiener, M.C. (登録日: 2003-01-21, 公開日: 2003-04-29, 最終更新日: 2023-08-16)

主引用文献

CHIMENTO, D.P.,MOHANTY, A.K.,KADNER, R.J.,WIENER, M.C.
Substrate-induced transmembrane signaling in the cobalamin transporter BtuB
Nat.Struct.Biol., 10:394-401, 2003

PubMed Abstract: 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.

PubMed: 12652322
DOI: 10.1038/nsb914

実験手法

X-RAY DIFFRACTION (3.31 Å)