6AN5

Crystal Structure of The Nucelotide Binding Domain of an O-antigen polysaccharide ABC-transporter

Summary for 6AN5

• Entry DOI: 10.2210/pdb6an5/pdb
• Descriptor: ABC transporter (1 entity in total)
• Functional Keywords: nucleotide binding domain of abct4, transport protein
• Biological source: Aquifex aeolicus (strain VF5)
• Total number of polymer chains: 2
• Total formula weight: 55320.20

Authors

Zimmer, J.,Bi, Y. (deposition date: 2017-08-12, release date: 2017-11-29, Last modification date: 2024-03-13)

Primary citation

Bi, Y.,Mann, E.,Whitfield, C.,Zimmer, J.
Architecture of a channel-forming O-antigen polysaccharide ABC transporter.
Nature, 553:361-365, 2018

PubMed Abstract: O-antigens are cell surface polysaccharides of many Gram-negative pathogens that aid in escaping innate immune responses. A widespread O-antigen biosynthesis mechanism involves the synthesis of the lipid-anchored polymer on the cytosolic face of the inner membrane, followed by transport to the periplasmic side where it is ligated to the lipid A core to complete a lipopolysaccharide molecule. In this pathway, transport to the periplasm is mediated by an ATP-binding cassette (ABC) transporter, called Wzm-Wzt. Here we present the crystal structure of the Wzm-Wzt homologue from Aquifex aeolicus in an open conformation. The transporter forms a transmembrane channel that is sufficiently wide to accommodate a linear polysaccharide. Its nucleotide-binding domain and a periplasmic extension form 'gate helices' at the cytosolic and periplasmic membrane interfaces that probably serve as substrate entry and exit points. Site-directed mutagenesis of the gates impairs in vivo O-antigen secretion in the Escherichia coli prototype. Combined with a closed structure of the isolated nucleotide-binding domains, our structural and functional analyses suggest a processive O-antigen translocation mechanism, which stands in contrast to the classical alternating access mechanism of ABC transporters.

PubMed: 29320481
DOI: 10.1038/nature25190

Experimental method

X-RAY DIFFRACTION (3.512 Å)