Virulence effector that plays a role in hijacking the host vesicular trafficking by recruiting the small guanosine triphosphatase (GTPase) Rab1 to the cytosolic face of the Legionella-containing vacuole (LCVs). Acts as a phosphocholine hydrolase by mediating the hydrolysis of phosphocholine to Ser residues of host RAB1 (RAB1A, RAB1B or RAB1C). Dephosphocholination of target proteins restores accessibility to GTPase effector LepB. Can act on both GDP-bound and GTP-bound Rab proteins. [Rab1 protein]-O-phosphocholine-L-serine + H2O = [Rab1 protein]-L-serine + H(+) + phosphocholine Translocated into the host cell via the type IV secretion system (T4SS).