1N4A

The Ligand Bound Structure of E.coli BtuF, the Periplasmic Binding Protein for Vitamin B12

1N4A の概要

• エントリーDOI: 10.2210/pdb1n4a/pdb
• 関連するPDBエントリー: 1BMT 1EFD 1n4d
• 分子名称: Vitamin B12 transport protein btuF, CYANOCOBALAMIN (3 entities in total)
• 機能のキーワード: abc transporter, periplasmic binding protein, vitamin b12, transmembrane transport, structural genomics, psi, protein structure initiative, northeast structural genomics consortium, nesg, transport protein
• 由来する生物種: Escherichia coli
• 細胞内の位置: Periplasm : P37028
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 58994.11

構造登録者

Karpowich, N.K.,Smith, P.C.,Hunt, J.F.,Northeast Structural Genomics Consortium (NESG) (登録日: 2002-10-30, 公開日: 2003-03-11, 最終更新日: 2024-10-30)

主引用文献

Karpowich, N.K.,Huang, H.H.,Smith, P.C.,Hunt, J.F.
Crystal structures of the BtuF periplasmic-binding protein for vitamin B12 suggest a functionally important reduction in protein mobility upon ligand binding.
J.Biol.Chem., 278:8429-8434, 2003

PubMed Abstract: BtuF is the periplasmic binding protein (PBP) for the vitamin B12 transporter BtuCD, a member of the ATP-binding cassette (ABC) transporter superfamily of transmembrane pumps. We have determined crystal structures of Escherichia coli BtuF in the apo state at 3.0 A resolution and with vitamin B12 bound at 2.0 A resolution. The structure of BtuF is similar to that of the FhuD and TroA PBPs and is composed of two alpha/beta domains linked by a rigid alpha-helix. B12 is bound in the "base-on" or vitamin conformation in a wide acidic cleft located between these domains. The C-terminal domain shares structural homology to a B12-binding domain found in a variety of enzymes. The same surface of this domain interacts with opposite surfaces of B12 when comparing ligand-bound structures of BtuF and the homologous enzymes, a change that is probably caused by the obstruction of the face that typically interacts with this domain by the base-on conformation of vitamin B12 bound to BtuF. There is no apparent pseudo-symmetry in the surface properties of the BtuF domains flanking its B12 binding site even though the presumed transport site in the previously reported crystal structure of BtuCD is located in an intersubunit interface with 2-fold symmetry. Unwinding of an alpha-helix in the C-terminal domain of BtuF appears to be part of conformational change involving a general increase in the mobility of this domain in the apo structure compared with the B12-bound structure. As this helix is located on the surface likely to interact with BtuC, unwinding of the helix upon binding to BtuC could play a role in triggering release of B12 into the transport cavity. Furthermore, the high mobility of this domain in free BtuF could provide an entropic driving force for the subsequent release of BtuF required to complete the transport cycle.

PubMed: 12468528
DOI: 10.1074/jbc.M212239200

実験手法

X-RAY DIFFRACTION (2 Å)