PDBsum entry 7abp

Binding proteins

PDB id: 7abp

Contents

Protein chain

305 a.a. *

Ligands

FCA-FCB

Waters ×193

* Residue conservation analysis

PDB id:

7abp

Name:

Binding proteins

Title:

Sugar-binding and crystallographic studies of an arabinose-binding protein mutant (met108leu) which exhibits enhanced affinity and altered specificity

Structure:

L-arabinose-binding protein. Chain: a. Engineered: yes

Source:

Escherichia coli. Organism_taxid: 562

Resolution:

1.67Å R-factor: 0.162

Authors:

P.S.Vermersch,J.J.G.Tesmer,F.A.Quiocho

Key ref:

P.S.Vermersch et al. (1991). Sugar-binding and crystallographic studies of an arabinose-binding protein mutant (Met108Leu) that exhibits enhanced affinity and altered specificity. Biochemistry, 30, 6861-6866. PubMed id: 2069949 DOI: 10.1021/bi00242a009

Date:

25-Apr-91 Release date: 15-Oct-91

Protein chain

P02924  (ARAF_ECOLI) -  L-arabinose-binding periplasmic protein from Escherichia coli (strain K12)

Seq: 329 a.a.

Struc: 305 a.a.*

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

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1021/bi00242a009

Biochemistry 30:6861-6866 (1991)

PubMed id: 2069949

Sugar-binding and crystallographic studies of an arabinose-binding protein mutant (Met108Leu) that exhibits enhanced affinity and altered specificity.

P.S.Vermersch, D.D.Lemon, J.J.Tesmer, F.A.Quiocho.

ABSTRACT

In addition to hydrogen bonds, van der Waals forces contribute to the affinity of protein-carbohydrate interactions. Nonpolar van der Waals contacts in the complexes of the L-arabinose-binding protein (ABP) with monosaccharides have been studied by means of site-directed mutagenesis, equilibrium and rapid kinetic binding techniques, and X-ray crystallography. ABP, a periplasmic transport receptor of Escherichia coli, binds L-arabinose, D-galactose, and D-fucose with preferential affinity in the order of Ara greater than Gal much greater than Fuc. Well-refined, high-resolution structures of ABP complexed with the three sugars revealed that the structural differences in the ABP-sugar complexes are localized around C5 of the sugars, where the equatorial H of Ara has been substituted for CH3 (Fuc) or CH2OH (Gal). The side chain of Met108 undergoes a sterically dictated, ligand-specific, conformational change to optimize nonpolar interactions between its methyl group and the sugar. We found that the Met108Leu ABP binds Gal tighter than wild-type ABP binds Ara and exhibits a preference for ligand in the order of Gal much greater than Fuc greater than Ara. The differences in affinity can be attributed to differences in the dissociation rates of the ABP-sugar complexes. We have refined at better than 1.7-A resolution the crystal structures of the Met108Leu ABP complexed with each of the sugars and offer a molecular explanation for the altered binding properties.