Targeting of the arf-like GTPase Arl3p to the Golgi requires N-terminal acetylation and the membrane protein Sys1p

The GTPase Arl3p is required to recruit a second GTPase, ArI1p, to the Golgi in Saccharomyces cerevisiae. ArI1p binds to the GRIP domain, which is present in a number of long coiled-coil proteins or 'golgins'. Here we show that Arl3p is not myristoylated like most members of the Arf family, but is instead amino-terminally acetylated by the NatC complex. Targeting of Arl3p also requires a Golgi membrane protein Sys1p. The human homologues of Arl3p (Arf-related protein 1 (ARFRP1)) and Sys1p (hSys1) can be isolated in a complex after chemical cross-linking. This suggests that the targeting of ARFRP1/Arl3p to the Golgi is mediated by a direct interaction between its acetylated N terminus and Sys1p/hSys1.