PDBsum entry 9abp

Binding proteins

PDB id: 9abp

Contents

Protein chain

305 a.a. *

Ligands

GLA

GAL

Waters ×174

* Residue conservation analysis

PDB id:

9abp

Name:

Binding proteins

Title:

A pro to gly mutation in the hinge of the arabinose-binding protein enhances binding and alters specificity: sugar-binding and crystallographic studies

Structure:

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

Source:

Escherichia coli. Organism_taxid: 562

Resolution:

1.97Å R-factor: 0.180

Authors:

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

Key ref:

P.S.Vermersch et al. (1990). A Pro to Gly mutation in the hinge of the arabinose-binding protein enhances binding and alters specificity. Sugar-binding and crystallographic studies. J Biol Chem, 265, 16592-16603. PubMed id: 2204627

Date:

15-Nov-91 Release date: 15-Jan-92

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)

J Biol Chem 265:16592-16603 (1990)

PubMed id: 2204627

A Pro to Gly mutation in the hinge of the arabinose-binding protein enhances binding and alters specificity. Sugar-binding and crystallographic studies.

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

ABSTRACT

The L-arabinose-binding protein (ABP) of Escherichia coli consists structurally of two distinct globular domains connected by a hinge of three separate peptide segments. Arabinose is bound and completely sequestered within the deep cleft between the two domains. With reduced affinity, ABP also binds D-galactose (approximately 2-fold reduction) and D-fucose (approximately 40-fold reduction). Experiments have been conducted to explore the role in sugar binding of the hinge connecting the two domains of ABP. To increase the flexibility of the hinge region, a glycine was substituted for a proline at position 254 by site-directed mutagenesis. Unexpectedly, this mutation resulted in the dramatic enhancement of galactose binding over that of arabinose. The affinity of the mutant ABP for galactose increased by over 20-fold, while that for arabinose and fucose remained relatively unchanged. We have measured association and dissociation rates of the Gly-254 ABP with L-arabinose, D-galactose, and D-fucose and have determined the crystallographic structure of the protein complexed with each of the three sugars. Both the ligand-binding kinetic measurements and structure analysis indicate that the altered specificity is due to an effective increase in the rigidity of the hinge in the closed conformation which is induced upon galactose binding. Stabilizing contacts are formed between the strands of the hinge in the Gly-254 ABP when galactose is bound which are not found in complexes with the other sugars or the liganded wild-type protein.