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Publication Abstract from PubMed

Polysaccharides play critical roles in bacteria, including the formation of protective capsules and biofilms and establishing specific host cell interactions. Their transport across membranes is often mediated by ATP-binding cassette (ABC) transporters, which utilize ATP to translocate diverse molecules. Cyclic beta-glucans (CbetaGs) are critical for host interaction of the Rhizobiales, including the zoonotic pathogen Brucella. CbetaGs are exported into the periplasmic space by the cyclic glucan transporter (Cgt). The interaction of an ABC transporter with a polysaccharide substrate has not been visualized so far. Here we use single-particle cryoelectron microscopy to elucidate the structures of Cgt from Brucella abortus in four conformational states. The substrate-bound structure reveals an unusual binding pocket at the height of the cytoplasmic leaflet, whereas ADP-vanadate models hint at an alternative mechanism of substrate release. Our work provides insights into the translocation of large, heterogeneous substrates and sheds light on protein-polysaccharide interactions in general.

Mechanism of cyclic beta-glucan export by ABC transporter Cgt of Brucella.,Sedzicki J, Ni D, Lehmann F, Wu N, Zenobi R, Jung S, Stahlberg H, Dehio C Nat Struct Mol Biol. 2022 Dec;29(12):1170-1177. doi: 10.1038/s41594-022-00868-7. , Epub 2022 Dec 1. PMID:36456825^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.