The proteasome is a multisubunit structure that degrades proteins. Protein degradation is an essential component of regulation because proteins can become misfolded, damaged, or unnecessary. Proteasomes and their homologues vary greatly in complexity: from HslV (heat shock locus v), which is encoded by 1 gene in bacteria, to the eukaryotic 20S proteasome, which is encoded by more than 14 genes [1]. Recently evidence of two novel groups of bacterial proteasomes was proposed. The first is Anbu, which is sparsely distributed among cyanobacteria and proteobacteria [1]. The second is call beta-proteobacteria proteasome homologue (BPH) [1].

1: Rethinking proteasome evolution: two novel bacterial proteasomes. Valas RE, Bourne PE; J Mol Evol. 2008;66:494-504. PMID:18389302