This domain normally occurs as tandem repeats; however it is found as a single copy in the S. cerevisiae DNA-binding nuclear protein YCR593 (Swiss:P25357). This protein is involved in sporulation part of the SET3C complex, which is required to repress early/middle sporulation genes during meiosis ([2]). The bacterial proteins are likely to be involved in a cell wall function as they are found in conjunction with the Pfam:PF07501 domain, which is involved in various cell surface processes. This domain is also present in the resuscitation-promoting factors RpfB from Mycobacterium tuberculosis and Rpf2 from Corynebacterium glutamicum. These are factors that stimulate resuscitation of dormant cells [3]. This domain has a beta grasp fold. Structural description of this domain revealed a structural conservation between these domains and ubiquitin, hence it is termed UBL-G5 [4].

1: New Knowledge from Old: In silico discovery of novel protein domains in Streptomyces coelicolor. Yeats C, Bentley S, Bateman A; BMC Microbiol 2003;3:3-3. PMID:12625841

2: The S. cerevisiae SET3 complex includes two histone deacetylases, Hos2 and Hst1, and is a meiotic-specific repressor of the sporulation gene program. Pijnappel WW, Schaft D, Roguev A, Shevchenko A, Tekotte H, Wilm M, Rigaut G, Seraphin B, Aasland R, Stewart AF; Genes Dev 2001;15:2991-3004. PMID:11711434

3: Resuscitation-promoting factors as lytic enzymes for bacterial growth and signaling. Kana BD, Mizrahi V; FEMS Immunol Med Microbiol. 2010;58:39-50. PMID:19799629

4: The structure of Resuscitation promoting factor B from M. tuberculosis reveals unexpected ubiquitin-like domains. Ruggiero A, Squeglia F, Romano M, Vitagliano L, De Simone A, Berisio R; Biochim Biophys Acta. 2016;1860:445-451. PMID:26549874