This subdomain is found in the Rab1 GTPase-activating protein (GAP) domain of GAP LepB present in Legionella pneumophilia. LepB inactivates Rab1, a key regulator of the secretory vesicular trafficking machinery, by acting as a GTPase-activating protein. LepB is also an antagonist of DrrA, which promotes Rab1. LepB acts by an atypical RabGAP mechanism that is reminiscent of classical GAPs. This is the C-terminal subdomain of the GAP domain and consists of an unusual fold [1].

1: Mechanism of Rab1b deactivation by the Legionella pneumophila GAP LepB. Mihai Gazdag E, Streller A, Haneburger I, Hilbi H, Vetter IR, Goody RS, Itzen A; EMBO Rep. 2013;14:199-205. PMID:23288104