PDBsum entry 1fqb

Sugar binding protein

PDB id: 1fqb

Contents

Protein chain

370 a.a. *

Ligands

SOR-GLC-GLC

Waters ×562

* Residue conservation analysis

PDB id:

1fqb

Name:

Sugar binding protein

Title:

Structure of maltotriotol bound to open-form maltodextrin binding protein in p2(1)crystal form

Structure:

Maltodextrin-binding protein. Chain: a. Synonym: maltose-binding periplasmic protein, mmbp. Engineered: yes

Source:

Escherichia coli. Organism_taxid: 562. Expressed in: escherichia coli. Expression_system_taxid: 562

Resolution:

1.90Å R-factor: 0.162 R-free: 0.218

Authors:

X.Duan,J.A.Hall,H.Nikaido,F.A.Quiocho

Key ref:

X.Duan et al. (2001). Crystal structures of the maltodextrin/maltose-binding protein complexed with reduced oligosaccharides: flexibility of tertiary structure and ligand binding. J Mol Biol, 306, 1115-1126. PubMed id: 11237621 DOI: 10.1006/jmbi.2001.4456

Date:

04-Sep-00 Release date: 14-Mar-01

Protein chain

P0AEX9  (MALE_ECOLI) -  Maltose/maltodextrin-binding periplasmic protein from Escherichia coli (strain K12)

Seq: 396 a.a.

Struc: 370 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1006/jmbi.2001.4456

J Mol Biol 306:1115-1126 (2001)

PubMed id: 11237621

Crystal structures of the maltodextrin/maltose-binding protein complexed with reduced oligosaccharides: flexibility of tertiary structure and ligand binding.

X.Duan, J.A.Hall, H.Nikaido, F.A.Quiocho.

ABSTRACT

The structure of the maltodextrin or maltose-binding protein, an initial receptor for bacterial ABC-type active transport and chemotaxis, consists of two globular domains that are separated by a groove wherein the ligand is bound and enclosed by an inter-domain rotation. Here, we report the determination of the crystal structures of the protein complexed with reduced maltooligosaccharides (maltotriitol and maltotetraitol) in both the "closed" and "open" forms. Although these modified sugars bind to the receptor, they are not transported by the wild-type transporter. In the closed structures, the reduced sugars are buried in the groove and bound by both domains, one domain mainly by hydrogen-bonding interactions and the other domain primarily by non-polar interactions with aromatic side-chains. In the open structures, which abrogate both cellular activities of active transport and chemotaxis because of the large separation between the two domains, the sugars are bound almost exclusively to the domain rich in aromatic residues. The binding site for the open chain glucitol residue extends to a subsite that is distinct from those for the glucose residues that were uncovered in prior structural studies of the binding of active linear maltooligosaccharides. Occupation of this subsite may also account for the inability of the reduced oligosaccharides to be transported. The structures reported here, combined with those previously determined for several other complexes with active oligosaccharides in the closed form and with cyclodextrin in the open form, revealed at least four distinct modes of ligand binding but with only one being functionally active. This versatility reflects the flexibility of the protein, from very large motions of interdomain rotation to more localized side-chain conformational changes, and adaptation by the oligosaccharides as well.

Selected figure(s)

Figure 2.
Figure 2. Binding of maltotriitol to the MBP closed form in the C2 space group crystal. The sugar residues are labeled -G1 for the glucitol, followed by G1, G2, and G3 for the glucose residues. (a) Difference (F[o] -F[c]) omit electron density map (blue) at 2.3 Å resolution of the maltotriitol contoured at 2s level. (b) Stereo view of the hydrogen bonds ( slant 3.4 Å) (broken lines) and stacking interactions between the maltotriitol and MBP. With the exception of E111 and E153, all the polar residues (blue color) that are involved in hydrogen-bonding interactions originate from domain I. E111 and E153 (red color) are located in domain II and the hinge connecting the two domains, respectively. The aromatic residues (colored green) originate from domain I (W62) and domain II (W230, Y155, W340).

Figure 3.
Figure 3. The binding site of MBP with bound maltotetraitol in the C2 or closed structure. The identifications of the amino acid residues and the sugar residues are identical with those shown in Figure 2. The additional Tyr341 residue originates from domain II. (a) The 2.3 Å difference electron density map of maltotetraitol patterned after Figure 2(a). (b) Stereo view of the hydrogen bonds ( slant 3.4 Å) (broken lines) and stacking interactions.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2001, 306, 1115-1126) copyright 2001.

Figures were selected by an automated process.