This domain is found in Antitoxin SocA from Caulobacter vibrioides and in similar proteins widespread across bacteria, archaea and tailed bacteriophages. SocA is the antitoxin component of an atypical type II toxin-antitoxin (TA) system which neutralises the toxic activity of toxin SocB by acting as an adapter to promote its degradation by the protease ClpXP [1,2].

1: A hyperpromiscuous antitoxin protein domain for the neutralization of diverse toxin domains. Kurata T, Saha CK, Buttress JA, Mets T, Brodiazhenko T, Turnbull KJ, Awoyomi OF, Oliveira SRA, Jimmy S, Ernits K, Delannoy M, Persson K, Tenson T, Strahl H, Hauryliuk V, Atkinson GC; Proc Natl Acad Sci U S A. 2022; [Epub ahead of print] PMID:35121656

2: A bacterial toxin inhibits DNA replication elongation through a direct interaction with the beta sliding clamp. Aakre CD, Phung TN, Huang D, Laub MT; Mol Cell. 2013;52:617-628. PMID:24239291