PDBsum entry 4xtc

Transport protein

PDB id: 4xtc

Contents

Protein chains

288 a.a.

287 a.a.

363 a.a.

492 a.a.

Ligands

BEM-BEM-BEM-BEM-BEM

PDB id:

4xtc

Name:

Transport protein

Title:

Crystal structure of bacterial alginate abc transporter in complex with alginate pentasaccharide-bound periplasmic protein

Structure:

Algm1. Chain: m. Engineered: yes. Mutation: yes. Algm2. Chain: n. Engineered: yes. Algs. Chain: s, t.

Source:

Sphingomonas sp. A1. Organism_taxid: 90322. Strain: a1. Gene: algm1. Expressed in: escherichia coli. Expression_system_taxid: 562. Gene: algm2. Gene: algs. Gene: algq2.

Resolution:

3.60Å R-factor: 0.241 R-free: 0.289

Authors:

A.Kaneko,Y.Maruyama,N.Mizuno,S.Baba,T.Kumasaka,B.Mikami,K.Murata, W.Hashimoto

Key ref:

A.Kaneko et al. (2017). A solute-binding protein in the closed conformation induces ATP hydrolysis in a bacterial ATP-binding cassette transporter involved in the import of alginate. J Biol Chem, 292, 15681-15690. PubMed id: 28768763

Date:

23-Jan-15 Release date: 02-Mar-16

Protein chain

Q9KWT8  (Q9KWT8_SPHSX) -  AlgM1 from Sphingomonas sp

Seq: 324 a.a.

Struc: 288 a.a.

Protein chain

Q9KWT7  (Q9KWT7_SPHSX) -  AlgM2 from Sphingomonas sp

Seq: 293 a.a.

Struc: 287 a.a.

Protein chains

Q9KWT9  (Q9KWT9_SPHSX) -  AlgS from Sphingomonas sp

Seq: 363 a.a.

Struc: 363 a.a.*

Protein chain

Q9KWT5  (Q9KWT5_SPHSX) -  AlgQ2 from Sphingomonas sp

Seq: 516 a.a.

Struc: 492 a.a.

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

J Biol Chem 292:15681-15690 (2017)

PubMed id: 28768763

A solute-binding protein in the closed conformation induces ATP hydrolysis in a bacterial ATP-binding cassette transporter involved in the import of alginate.

A.Kaneko, K.Uenishi, Y.Maruyama, N.Mizuno, S.Baba, T.Kumasaka, B.Mikami, K.Murata, W.Hashimoto.

ABSTRACT

The Gram-negative bacteriumSphingomonassp. A1 incorporates alginate into cells via the cell-surface pit without prior depolymerization by extracellular enzymes. Alginate import across cytoplasmic membranes thereby depends on the ATP-binding cassette transporter AlgM1M2SS (a heterotetramer of AlgM1, AlgM2, and AlgS), which cooperates with the periplasmic solute-binding protein AlgQ1 or AlgQ2; however, several details of AlgM1M2SS-mediated alginate import are not well-understood. Herein, we analyzed ATPase and transport activities of AlgM1M2SS after reconstitution into liposomes with AlgQ2 and alginate oligosaccharide substrates having different polymerization degrees (PDs). Longer alginate oligosaccharides (PD ≥ 5) stimulated the ATPase activity of AlgM1M2SS but were inert as substrates of AlgM1M2SS-mediated transport, indicating that AlgM1M2SS-mediated ATP hydrolysis can be stimulated independently of substrate transport. Using X-ray crystallography in the presence of AlgQ2 and long alginate oligosaccharides (PD 6-8) and with the humid air and glue-coating method, we determined the crystal structure of AlgM1M2SS in complex with oligosaccharide-bound AlgQ2 at 3.6 Å resolution. The structure of the ATP-binding cassette transporter in complex with non-transport ligand-bound periplasmic solute-binding protein revealed that AlgM1M2SS and AlgQ2 adopt inward-facing and closed conformations, respectively. Thesein vitroassays and structural analyses indicated that interactions between AlgM1M2SS in the inward-facing conformation and periplasmic ligand-bound AlgQ2 in the closed conformation induce ATP hydrolysis by the ATP-binding protein AlgS. We conclude that substrate-bound AlgQ2 in the closed conformation initially interacts with AlgM1M2SS, the AlgM1M2SS-AlgQ2 complex then forms, and this formation is followed by ATP hydrolysis.