PDBsum entry 1y3q

Sugar binding protein

PDB id: 1y3q

Contents

Protein chain

490 a.a. *

Metals

_CA

Waters ×325

* Residue conservation analysis

PDB id:

1y3q

Name:

Sugar binding protein

Title:

Structure of algq1, alginate-binding protein

Structure:

Algq1. Chain: a. Fragment: residues 1-490. Synonym: alginate-binding protein. Engineered: yes

Source:

Sphingomonas sp.. Organism_taxid: 90322. Strain: a1. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.90Å R-factor: 0.194 R-free: 0.244

Authors:

K.Momma,Y.Mishima,W.Hashimoto,B.Mikami,K.Murata

Key ref:

K.Momma et al. (2005). Direct evidence for Sphingomonas sp. A1 periplasmic proteins as macromolecule-binding proteins associated with the ABC transporter: molecular insights into alginate transport in the periplasm. Biochemistry, 44, 5053-5064. PubMed id: 15794643 DOI: 10.1021/bi047781r

Date:

26-Nov-04 Release date: 12-Apr-05

Protein chain

Q9KWT6  (Q9KWT6_SPHSX) -  AlgQ1 from Sphingomonas sp

Seq: 526 a.a.

Struc: 490 a.a.

DOI no: 10.1021/bi047781r

Biochemistry 44:5053-5064 (2005)

PubMed id: 15794643

Direct evidence for Sphingomonas sp. A1 periplasmic proteins as macromolecule-binding proteins associated with the ABC transporter: molecular insights into alginate transport in the periplasm.

K.Momma, Y.Mishima, W.Hashimoto, B.Mikami, K.Murata.

ABSTRACT

A Gram-negative bacterium, Sphingomonas sp. A1, has a macromolecule (alginate) import system consisting of a pit on the cell surface and an alginate-specific ATP-binding cassette importer in the inner membrane. Transport of alginate from the pit to the ABC importer is probably mediated by two periplasmic binding protein homologues (AlgQ1 and AlgQ2). Here we describe characteristics of binding of AlgQ1 and AlgQ2 to alginate and its oligosaccharides through surface plasmon resonance biosensor analysis, UV absorption difference spectroscopy, and X-ray crystallography. Both AlgQ1 and AlgQ2 were inducibly expressed in the periplasm of alginate-grown cells of strain A1. Biosensor analysis indicated that both proteins specifically bind alginate with a high degree of polymerization (>100) and that dissociation constants for alginate with an average molecular mass of 26 kDa are 2.3 x 10(-)(7) M for AlgQ1 and 1.5 x 10(-)(7) M for AlgQ2. An in vitro ATPase assay using the membrane complex, including the alginate ABC importer, suggested that both alginate-bound forms of AlgQ1 and AlgQ2 are closely associated with the importer. X-ray crystallography showed that AlgQ1 consisted of two domains separated by a deep cleft that binds alginate oligosaccharides through a conformational change in the two domains. These results directly show that alginate-binding proteins play an important role in the efficient transport of alginate macromolecules with different degrees of polymerization in the periplasm.