GBF1 recruits inactive ARF:GDP complexes to the ERGIC (Monetta et al, 2007). There are 5 known ADP-ribosylation factor proteins (ARFs) in the human cell. Class I members ARF1 and ARF 3 are expressed at high levels and broadly distributed through the secretory system, while Class II members ARF4 and ARF5 are expressed at lower levels, with ARF4 showing the most specific localization to the ERGIC compartment. ARF6, the single Class III ARF, appears to function more specifically in endocytosis and actin dynamics (Chun et al, 2008; reviewed in D'Souza-Schorey and Chavrier, 2006; Szul and Sztul, 2011). There is conflicting evidence regarding what ARF(s) is required at the ERGIC membrane. GBF1 has been shown to activate ARF1, 4, and 5, but not ARF3, while single and pairwise knockdown of ARF1, 3, 4 and 5 suggests that although no single ARF is responsible for any given step in the secretory pathway, ARF1 and ARF3 contribute most specifically to the ERGIC-Golgi step (Manolea et al, 2010; Volpicelli-Daley et al, 2005). Recruitment of ARF at may also be facilitated by interaction with p24 family members (Gommel et al, 2001; reviewed in Schuiki and Volchuk, 2012).