This family consists of several Toluene-4-monooxygenase system protein B (TmoB) sequences. Pseudomonas mendocina KR1 metabolises toluene as a carbon source. The initial step of the pathway is hydroxylation of toluene to form p-cresol by a multicomponent toluene-4-monooxygenase (T4MO) system [1]. TmoB adopts a ubiquitin fold [2]. Although TmoB is a component of the T4MO system, its precise role remains unclear.

1: Cloning and characterization of a Pseudomonas mendocina KR1 gene cluster encoding toluene-4-monooxygenase. Yen KM, Karl MR, Blatt LM, Simon MJ, Winter RB, Fausset PR, Lu HS, Harcourt AA, Chen KK; J Bacteriol 1991;173:5315-5327. PMID:1885512

2: The prokaryotic antecedents of the ubiquitin-signaling system and the early evolution of ubiquitin-like beta-grasp domains. Iyer LM, Burroughs AM, Aravind L; Genome Biol. 2006;7:R60. PMID:16859499