This domain is found in bacteria, archaea and eukaryotes, and is approximately 50 amino acids in length. It contains an evolutionary conserved signature W-X-Y-X6-11-GPF-X4-M-X2-W-X3-GYF, the site of interaction with proline-rich peptides. Family members include RME-8 (Required for receptor-mediated endocytosis 8), a DNAJC13 protein. RME-8 was first identified as a protein that is required for endocytosis in Caenorhabditis elegans. It coordinates the activity of the WASH complex with the function of the retromer SNX dimer to control endosomal tubulation [1]. Family members found in Arabidopsis include Arabidopsis trithorax-related3 (Atxr3), also known as set domain group 2 (Sdg2). It is the major enzyme responsible for H3K4me3 in Arabidopsis and SDG2-dependent H3K4m3 is critical for regulating gene expression and plant development [2]. Another family member found in Arabidopsis is Tic56. It is an essential subunit of a 1-MDa protein complex at the inner chloroplast envelope membrane [3]. Furthermore, Tic56 is important for rRNA processing and chloroplast ribosome assembly [4].

1: RME-8 coordinates the activity of the WASH complex with the function of the retromer SNX dimer to control endosomal tubulation. Freeman CL, Hesketh G, Seaman MN; J Cell Sci. 2014;127:2053-2070. PMID:24643499

2: SET DOMAIN GROUP2 is the major histone H3 lysine [corrected] 4 trimethyltransferase in Arabidopsis. Guo L, Yu Y, Law JA, Zhang X; Proc Natl Acad Sci U S A. 2010;107:18557-18562. PMID:20937886

3: Protein import-independent functions of Tic56, a component of the 1-MDa translocase at the inner chloroplast envelope membrane. Agne B, Kohler D, Baginsky S; Plant Signal Behav. 2017;12:e1284726. PMID:28125316

4: Importance of Translocon Subunit Tic56 for rRNA Processing and Chloroplast Ribosome Assembly. Kohler D, Helm S, Agne B, Baginsky S; Plant Physiol. 2016;172:2429-2444. PMID:27733515