This family contains the bacterial protein TrbM (approximately 180 residues long). In Comamonas testosteroni T-2, TrbM is derived from the IncP1beta plasmid pTSA, which encodes the widespread genes for p-toluenesulfonate (TSA) degradation [1]. This family also includes MPFK and its functional homologue kikA, which are required for efficient conjugative transfer in IncP-9 plasmids [2].

1: Map of the IncP1beta plasmid pTSA encoding the widespread genes (tsa) for p-toluenesulfonate degradation in Comamonas testosteroni T-2. Tralau T, Cook AM, Ruff J; Appl Environ Microbiol 2001;67:1508-1516. PMID:11282598

2: Conjugative Transfer of IncP-9 Catabolic Plasmids Requires a Previously Uncharacterized Gene, mpfK, Whose Homologs Are Conserved in Various MPFT-Type Plasmids. Kishida K, Nonoyama S, Lukas T, Kawahara S, Kudo K, Nagata Y, Ohtsubo Y, Tsuda M; Appl Environ Microbiol. 2019; [Epub ahead of print] PMID:31604768