Legionella pneumophila modulates the host metabolism of phosphoinositides (PIs) to impair membrane trafficking and establish the Legionella-containing vacuole (LCV) for its own replication. The virulence factor SidF is a unique PI phosphatase that specifically hydrolyses PI(3,4)P2 and PI(3,4,5)P3. This protein shows a large single domain that resembles a cowboy hat, which consists of 19 alpha-helices located around a 10-pleated beta-sheet core [1].

1: Structural basis for substrate recognition by a unique Legionella phosphoinositide phosphatase. Hsu F, Zhu W, Brennan L, Tao L, Luo ZQ, Mao Y; Proc Natl Acad Sci U S A. 2012;109:13567-13572. PMID:22872863