An uncharacterized alpha+beta fold domain that is mostly fused to a RimK-like ATP-grasp and is found in bacteria and euryarchaea. Members of this family are almost always associated in gene neighborhoods with a GNAT-like acetyltransferase fused to a papain-like petidase. Additionally M20-like peptidases, GCS2, 4Fe-4S Ferredoxins, a distinct metal-sulfur cluster protein and ribosomal proteins are found in the gene neighborhoods. Contextual analysis suggests a role for these in peptide biosynthesis [1].

1: Amidoligases with ATP-grasp, glutamine synthetase-like and acetyltransferase-like domains: synthesis of novel metabolites and peptide modifications of proteins. Iyer LM, Abhiman S, Maxwell Burroughs A, Aravind L; Mol Biosyst. 2009;5:1636-1660. PMID:20023723