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Updated: Mar 10, 2026

Conjugative Mating Assays for Sequence-specific Analysis of Transfer Proteins Involved in Bacterial Conjugation
Published on: January 4, 2017
Cag-delta (Cag3) protein from the Helicobacter pylori 26695 cag type IV secretion system forms ring-like
Jonathan Smart1, Aurélien Fouillen1,2, Bastien Casu1
1Department of Biochemistry and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montreal, QC H3C 3J7, Canada.
Abstract:
Helicobacter pylori is an important cause of gastric pathologies and persistent infection can lead to stomach cancer. Virulent H. pylori strains encode a type IV secretion system responsible for translocation of the oncogenic CagA protein into cells of the gastric mucosa. Gene HP0522 encodes the essential component Cagδ (Cag3), and we show by gel filtration and cross-linking that purified Cagδ forms high molecular mass complexes. In contrast, its interaction partner CagT is mostly monomeric, but co-fractionates after gel filtration. Analysis by transmission electron microscopy revealed that purified Cagδ complexes can self-assemble ring-like structures. Cagδ-overexpressing Escherichia coli exhibits membrane-associated circular profiles in regions of the cell envelope with intense immunogold labelling with a Cagδ-specific antiserum. Our results suggest that Cagδ has the capacity to form macromolecular structures contributing to the assembly of the type IV secretion system.
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