A domain of unknown function found in multiple copies in several archaebacterial proteins. Conserved N-terminal lysine and C-terminal asparagine with central asp/glu suggests that many of these domain may contain an isopeptide bond. In Methanothermobacter sp. CaT2, a DUF11-containing repeat hypothetical protein encoded by MTCT_1020 plays a key role as a membrane-bound adhesion protein in the aggregation of CaT2. DUF11-containing repeat domains are not involved in aggregation, but may be important for stabilizing the surface cell wall structures of CaT2 [1].

1: An Aggregation-defective Mutant of Methanothermobacter sp. CaT2 Reveals Unique Protein-dependent Aggregation. Sumikawa K, Kosaka T, Mayahara N, Matsutani M, Udo K, Yamada M; Microbes Environ. 2019;34:244-251. PMID:31189768