Structural Basis of Lipid Targeting and Destruction by the Type V Secretion System of Pseudomonas aeruginosa

J Mol Biol. 2016 May 8;428(9 Pt A):1790-803. doi: 10.1016/j.jmb.2016.03.012. Epub 2016 Mar 21.


The type V secretion system is a macromolecular machine employed by a number of bacteria to secrete virulence factors into the environment. The human pathogen Pseudomonas aeruginosa employs the newly described type Vd secretion system to secrete a soluble variant of PlpD, a lipase of the patatin-like family synthesized as a single macromolecule that also carries a polypeptide transport-associated domain and a 16-stranded β-barrel. Here we report the crystal structure of the secreted form of PlpD in its biologically active state. PlpD displays a classical lipase α/β hydrolase fold with a catalytic site located within a highly hydrophobic channel that entraps a lipidic molecule. The active site is covered by a flexible lid, as in other lipases, indicating that this region in PlpD must modify its conformation in order for catalysis at the water-lipid interface to occur. PlpD displays phospholipase A1 activity and is able to recognize a number of phosphatidylinositols and other phosphatidyl analogs. PlpD is the first example of an active phospholipase secreted through the type V secretion system, for which there are more than 200 homologs, revealing details of the lipid destruction arsenal expressed by P. aeruginosa in order to establish infection.

Keywords: bacterial secretion; crystallography; infection; lipid affinity; phospholipase.

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism*
  • Catalytic Domain
  • Crystallography, X-Ray
  • Models, Molecular
  • Phosphatidylinositols / metabolism
  • Phospholipases / chemistry*
  • Phospholipases / metabolism*
  • Protein Conformation
  • Pseudomonas aeruginosa / enzymology*
  • Substrate Specificity
  • Type V Secretion Systems / metabolism


  • Bacterial Proteins
  • Phosphatidylinositols
  • Type V Secretion Systems
  • Phospholipases