4XTC

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

Summary for 4XTC

• Entry DOI: 10.2210/pdb4xtc/pdb
• Descriptor: AlgM1, AlgM2, AlgS, ... (5 entities in total)
• Functional Keywords: abc, alginate, sphingomonas, transporter, transport protein
• Biological source: Sphingomonas sp. A1; More
• Total number of polymer chains: 5
• Total formula weight: 208519.57

Authors

Kaneko, A.,Maruyama, Y.,Mizuno, N.,Baba, S.,Kumasaka, T.,Mikami, B.,Murata, K.,Hashimoto, W. (deposition date: 2015-01-23, release date: 2016-03-02, Last modification date: 2023-11-08)

Primary citation

Kaneko, A.,Uenishi, K.,Maruyama, Y.,Mizuno, N.,Baba, S.,Kumasaka, T.,Mikami, B.,Murata, K.,Hashimoto, W.
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, 2017

PubMed Abstract: The Gram-negative bacterium sp. 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. These assays 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.

PubMed: 28768763
DOI: 10.1074/jbc.M117.793992

Experimental method

X-RAY DIFFRACTION (3.6 Å)