Y2h screening also identified PDES interacting proteins other than isoprenylated proteins, such as Arl2 and Arl3 (Hanzal-Bayer et al., 2002). So far, Arl2 and Arl3 are the only non-isoprenylated proteins shown capable of PDES interaction. Arl2 and Arl3 are also small GTPases belonging to the Arf family in the Ras superfamily. Arf family members play important roles in intracellular vesicular trafficking processes. Arl proteins differ from Arfs in that Arl proteins do not possess co-factor activity of cholera toxin-catalyzed ADP-ribosylation of Gas subunits. And unlike in Arfs, the glycine residue at position 2 in some Arls cannot be myristoylated (Sharer et al., 2002). The binding of PDES to Arl3 depends on the guanine nucleotide species bound to Arl3, and b-sheet interaction. PDES only interacts with GTP-bound Arl3, but not GDP-bound Arl3, suggesting PDES is one of the effectors of Arl3 GTPase (Linari et al., 1999a).
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