This is a domain found in PatG proteins, these proteins are involved in prfocessing the precursor peptide to yield the cyclic Patellamide. PatG can be found in Prochloron sp [1].

1: The structure of the cyanobactin domain of unknown function from PatG in the patellamide gene cluster. Mann G, Koehnke J, Bent AF, Graham R, Houssen W, Jaspars M, Schwarz-Linek U, Naismith JH; Acta Crystallogr F Struct Biol Commun. 2014;70:1597-1603. PMID:25484206