4KI0

Crystal structure of the maltose-binding protein/maltose transporter complex in an outward-facing conformation bound to maltohexaose

4KI0 の概要

• エントリーDOI: 10.2210/pdb4ki0/pdb
• 関連するPDBエントリー: 4KHZ
• 関連するBIRD辞書のPRD_ID: PRD_900010
• 分子名称: ABC transporter related protein, Maltose-binding periplasmic protein, Maltose transport system permease protein MalF, ... (10 entities in total)
• 機能のキーワード: abc transporter, atpase maltodextrin transporter, atp binding maltodextrin binding, inner membrane, transport protein
• 由来する生物種: Escherichia coli; 詳細
• タンパク質・核酸の鎖数: 5
• 化学式量合計: 224254.60

構造登録者

Oldham, M.L.,Chen, S.,Chen, J. (登録日: 2013-05-01, 公開日: 2013-10-23, 最終更新日: 2023-09-20)

主引用文献

Oldham, M.L.,Chen, S.,Chen, J.
Structural basis for substrate specificity in the Escherichia coli maltose transport system.
Proc.Natl.Acad.Sci.USA, 110:18132-18137, 2013

PubMed Abstract: ATP-binding cassette (ABC) transporters are molecular pumps that harness the chemical energy of ATP hydrolysis to translocate solutes across the membrane. The substrates transported by different ABC transporters are diverse, ranging from small ions to large proteins. Although crystal structures of several ABC transporters are available, a structural basis for substrate recognition is still lacking. For the Escherichia coli maltose transport system, the selectivity of sugar binding to maltose-binding protein (MBP), the periplasmic binding protein, does not fully account for the selectivity of sugar transport. To obtain a molecular understanding of this observation, we determined the crystal structures of the transporter complex MBP-MalFGK2 bound with large malto-oligosaccharide in two different conformational states. In the pretranslocation structure, we found that the transmembrane subunit MalG forms two hydrogen bonds with malto-oligosaccharide at the reducing end. In the outward-facing conformation, the transmembrane subunit MalF binds three glucosyl units from the nonreducing end of the sugar. These structural features explain why modified malto-oligosaccharides are not transported by MalFGK2 despite their high binding affinity to MBP. They also show that in the transport cycle, substrate is channeled from MBP into the transmembrane pathway with a polarity such that both MBP and MalFGK2 contribute to the overall substrate selectivity of the system.

PubMed: 24145421
DOI: 10.1073/pnas.1311407110

実験手法

X-RAY DIFFRACTION (2.38 Å)