This entry represents a HDS (homology downstream of Sec7) domain found towards the C-terminal of guanine nucleotide exchange factors involved Golgi transport, such as budding yeast protein Sec7, protein Mon2 and BIG1-like proteins [1,2]. Sec7 is involved in the secretory pathway as a protein binding scaffold for the COPII-COPI protein switch for maturation of the VTC intermediate compartments for Golgi compartment biogenesis [3]. Sec7 has four HDS1-4 domains, which act to integrate the signals from several small GTPases, including Arf1 itself, to switch Sec7 from a strongly autoinhibited to a strongly auto activated form [2].

1: Structural Insights into Arl1-Mediated Targeting of the Arf-GEF BIG1 to the trans-Golgi. Galindo A, Soler N, McLaughlin SH, Yu M, Williams RL, Munro S; Cell Rep. 2016;16:839-850. PMID:27373159

2: The Sec7 N-terminal regulatory domains facilitate membrane-proximal activation of the Arf1 GTPase. Richardson BC, Halaby SL, Gustafson MA, Fromme JC; Elife. 2016; [Epub ahead of print] PMID:26765562

3: Sec7p directs the transitions required for yeast Golgi biogenesis. Deitz SB, Rambourg A, Kepes F, Franzusoff A; Traffic. 2000;1:172-183. PMID:11208097