PDBsum entry 3l6h

Glycine betaine-binding protein

PDB id: 3l6h

Contents

Protein chain

254 a.a. *

Ligands

BET

Metals

_CL ×2

Waters ×140

* Residue conservation analysis

PDB id:

3l6h

Name:

Glycine betaine-binding protein

Title:

Crystal structure of lactococcal opuac in its closed-liganded conformation complexed with glycine betaine

Structure:

Betaine abc transporter permease and substrate binding protein. Chain: a. Fragment: substrate binding domain (unp residues 320-573). Engineered: yes

Source:

Lactococcus lactis. Streptococcus lactis. Organism_taxid: 1358. Strain: nz9000. Gene: busab, ll1451, l724, l72477. Expressed in: lactococcus lactis. Expression_system_taxid: 1358.

Resolution:

2.30Å R-factor: 0.198 R-free: 0.221

Authors:

R.P.A.Berntsson,J.C.Wolters,N.Gul,A.Karasawa,A.M.W.H.Thunnissen, D.J.Slotboom,B.Poolman

Key ref:

J.C.Wolters et al. (2010). Ligand binding and crystal structures of the substrate-binding domain of the ABC transporter OpuA. Plos One, 5, e10361. PubMed id: 20454456

Date:

23-Dec-09 Release date: 19-May-10

Protein chain

Q7DAU8  (Q7DAU8_LACLA) -  Betaine ABC transporter permease and substrate binding protein from Lactococcus lactis subsp. lactis (strain IL1403)

Seq: 573 a.a.

Struc: 254 a.a.

Plos One 5:e10361 (2010)

PubMed id: 20454456

Ligand binding and crystal structures of the substrate-binding domain of the ABC transporter OpuA.

J.C.Wolters, R.P.Berntsson, N.Gul, A.Karasawa, A.M.Thunnissen, D.J.Slotboom, B.Poolman.

ABSTRACT

BACKGROUND: The ABC transporter OpuA from Lactococcus lactis transports glycine betaine upon activation by threshold values of ionic strength. In this study, the ligand binding characteristics of purified OpuA in a detergent-solubilized state and of its substrate-binding domain produced as soluble protein (OpuAC) was characterized. PRINCIPAL FINDINGS: The binding of glycine betaine to purified OpuA and OpuAC (K(D) = 4-6 microM) did not show any salt dependence or cooperative effects, in contrast to the transport activity. OpuAC is highly specific for glycine betaine and the related proline betaine. Other compatible solutes like proline and carnitine bound with affinities that were 3 to 4 orders of magnitude lower. The low affinity substrates were not noticeably transported by membrane-reconstituted OpuA. OpuAC was crystallized in an open (1.9 A) and closed-liganded (2.3 A) conformation. The binding pocket is formed by three tryptophans (Trp-prism) coordinating the quaternary ammonium group of glycine betaine in the closed-liganded structure. Even though the binding site of OpuAC is identical to that of its B. subtilis homolog, the affinity for glycine betaine is 4-fold higher. CONCLUSIONS: Ionic strength did not affect substrate binding to OpuA, indicating that regulation of transport is not at the level of substrate binding, but rather at the level of translocation. The overlap between the crystal structures of OpuAC from L.lactis and B.subtilis, comprising the classical Trp-prism, show that the differences observed in the binding affinities originate from outside of the ligand binding site.