GTPase-activating protein specific for Rab1 and Rab2 small GTPase families for which it can accelerate the intrinsic GTP hydrolysis rate by more than five orders of magnitude. (Microbial infection) Directly interacts with the N-terminal amphipathic helix of hepatitis C virus (HCV) NS5A. The arginine and glutamine fingers are critical for the GTPase-activating mechanism, they pull out Rab's 'switch 2' glutamine and insert in Rab's active site. The disease is caused by variants affecting the gene represented in this entry. May be due to intron retention.