This is the C-terminal domain of RalF protein present in Legionella pneumophilia. RalF is secreted into host cytosol via the Dot/Icm type IV transporter where it acts to recruit ADP-ribosylation factor (Arf) to pathogen-containing phagosomes in the establishment of a replicative organelle. This domain forms a cap over the active site in the Sec7 domain and so is referred to as the Sec7-capping domain [1].

1: The structure of RalF, an ADP-ribosylation factor guanine nucleotide exchange factor from Legionella pneumophila, reveals the presence of a cap over the active site. Amor JC, Swails J, Zhu X, Roy CR, Nagai H, Ingmundson A, Cheng X, Kahn RA; J Biol Chem. 2005;280:1392-1400. PMID:15520000