| Affiliation: | (1) Argonne National Laboratory, Biosciences Division, Midwest Center for Structural Genomics and Structural Biology Center, 9700 S. Cass Ave., Argonne, IL 60439, USA;(2) University of Toronto, Structural Genomics Consortium, Toronto, Canada;(3) Clinical Genomics Centre/Proteomics, University Health Network, 200 Elizabeth St., Toronto, ON, M5G 1L7, Canada;(4) Department of Biochemistry and Molecular Biology, University of Chicago, 920 E. 58th St., Chicago, IL 60637, USA; |
| Abstract: | The Type VI secretion pathway transports proteins across the cell envelope of Gram-negative bacteria. Pseudomonas aeruginosa, an opportunistic Gram-negative bacterial pathogen infecting humans, uses the type VI secretion pathway to export specific effector proteins crucial for its pathogenesis. The HSI-I virulence locus encodes for several proteins that has been proposed to participate in protein transport including the Hcp1 protein, which forms hexameric rings that assemble into nanotubes in vitro. Two Hcp1 paralogues have been identified in the P. aeruginosa genome, Hsp2 and Hcp3. Here, we present the structure of the Hcp3 protein from P. aeruginosa. The overall structure of the monomer resembles Hcp1 despite the lack of amino-acid sequence similarity between the two proteins. The monomers assemble into hexamers similar to Hcp1. However, instead of forming nanotubes in head-to-tail mode like Hcp1, Hcp3 stacks its rings in head-to-head mode forming double-ring structures. |
