Here, we report the identification of a novel domain--GG (domain in KIAA1199, FAM3, POMGnT1 and Tmem2 proteins, with two well-conserved glycine residues), present in eukaryotic FAM3 superfamily (FAM3A, FAM3B, FAM3C and FAM3D), POMGnT1 (protein O-linked mannose beta-1,2-N-acetylglucosaminyltransferase), TEM2 proteins as well as phage gp35 proteins. GG domain has been revealed to be implicated in muscle-eye-brain disease and non-syndromic hearing loss. The presence of GG domain in Bacteriophage gp35 hinge connector of long tail fiber might reflect the horizontal gene transfer from organisms. And we proposed that GG domain might function as important structural element in phage LTF.