COG4 is a component of the conserved oligomeric Golgi (COG) complex which mediates the proper glycosylation of proteins trafficking through the Golgi apparatus. It is included in the CATCHR (complexes associated with tethering containing helical rods) family, which includes components of the exocyst, COG, GARP, and DSL1 complexes, sharing structural and functional features, such as the alpha-helical bundles at the C-terminal and a N-terminal coiled-coil region [2,3]. This is the C-terminal domain which contains the key Arginine residue that stabilises this domain and it is required for the proper glycosylation of cell surface proteins [1,4].

1: Structural basis for a human glycosylation disorder caused by mutation of the COG4 gene. Richardson BC, Smith RD, Ungar D, Nakamura A, Jeffrey PD, Lupashin VV, Hughson FM; Proc Natl Acad Sci U S A. 2009;106:13329-13334. PMID:19651599

2: Homology and Modular Evolution of CATCHR at the Origin of the Eukaryotic Endomembrane System. Santana-Molina C, Gutierrez F, Devos DP; Genome Biol Evol. 2021; [Epub ahead of print] PMID:34061181

3: Crystal structure of Sec10, a subunit of the exocyst complex. Chen J, Yamagata A, Kubota K, Sato Y, Goto-Ito S, Fukai S; Sci Rep. 2017;7:40909. PMID:28098232

4: A Recurrent De Novo Heterozygous COG4 Substitution Leads to Saul-Wilson Syndrome, Disrupted Vesicular Trafficking, and Altered Proteoglycan Glycosylation. Ferreira CR, Xia ZJ, Clement A, Parry DA, Davids M, Taylan F, Sharma P, Turgeon CT, Blanco-Sanchez B, Ng BG, Logan CV, Wolfe LA, Solomon BD, Cho MT, Douglas G, Carvalho DR, Bratke H, Haug MG, Phillips JB, Wegner J, Tiemeyer M, Aoki K, Nordgren A, Hammarsjo A, Duker AL, Rohena L, Hove HB, Ek J, Adams D, Tifft CJ, Onyekweli T, Weixel T, Macnamara E, Radtke K, Powis Z, Earl D, Gabriel M, Russi AHS, Brick L, Kozenko M, Tham E, Raymond KM, Phillips JA 3rd, Tiller GE, Wilson WG, Hamid R, Malicdan MCV, Nishimura G, Grigelioniene G, Jackson A, Westerfield M, Bober MB, Gahl WA, Freeze HH; Am J Hum Genet. 2018;103:553-567. PMID:30290151