Article

Journal of Structural and Functional Genomics

, Volume 12, Issue 1, pp 21-26

Crystal structure of secretory protein Hcp3 from Pseudomonas aeruginosa

  • Jerzy OsipiukAffiliated withArgonne National Laboratory, Biosciences Division, Midwest Center for Structural Genomics and Structural Biology Center
  • , Xiaohui XuAffiliated withUniversity of Toronto, Structural Genomics Consortium
  • , Hong CuiAffiliated withUniversity of Toronto, Structural Genomics Consortium
  • , Alexei SavchenkoAffiliated withUniversity of Toronto, Structural Genomics Consortium
  • , Aled EdwardsAffiliated withUniversity of Toronto, Structural Genomics ConsortiumClinical Genomics Centre/Proteomics, University Health Network Email author 
  • , Andrzej JoachimiakAffiliated withArgonne National Laboratory, Biosciences Division, Midwest Center for Structural Genomics and Structural Biology CenterDepartment of Biochemistry and Molecular Biology, University of Chicago Email author 

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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.

Keywords

Type VI (T6SS) secretion system Hcp3 Hcp1 X-ray crystallography Structural genomics