Members of this family are found in T4 RNaseH ribonuclease, and adopt a SAM domain-like fold, consisting of a bundle of four/five helices. These residues may have a role in providing a docking site for other proteins or enzymes in the replication fork [1].

1: Structure of bacteriophage T4 RNase H, a 5' to 3' RNA-DNA and DNA-DNA exonuclease with sequence similarity to the RAD2 family of eukaryotic proteins. Mueser TC, Nossal NG, Hyde CC; Cell. 1996;85:1101-1112. PMID:8674116