This family is one of the two different components of the RAG1-RAG2 V(D)J recombinase complex. The RAG complex, consisting of two RAG1 and two RAG2 proteins is a multi-protein complex that mediates DNA cleavage during V(D)J (variable-diversity-joining) recombination [2]. RAG1 mediates DNA-binding to the conserved recombination signal sequences (RSS) [3]. Many of the proteins in this family are fragments. Solution of the structure of the complex of RAG1 and RAG2 shows that each protein dimerises with itself and each pair then complexes together to from the RAG1-RAG2 V(D)J recombinase enzyme. The different structural elements in RAG1 for UniProtKB:P15919 are: an N-terminal nonamer-binding domain from residues 391-459; a dimerisation and DNA-binding domain from 459-515; an extended pre-RNase H domain from 515-588; the catalytic RNase H domain from 588-719; a ZnC2 domain from 719-791; and ZnH2 domain from 791-962; and a three-helix C-terminal domain from 962-1008 [4,5].

1: The recombination activation gene 1 (RAG1) of rainbow trout (Oncorhynchus mykiss): cloning, expression, and phylogenetic analysis. Hansen JD, Kaattari SL; Immunogenetics. 1995;42:188-195. PMID:7642230

2: RAG: a recombinase diversified. Matthews AG, Oettinger MA; Nat Immunol. 2009;10:817-821. PMID:19621044

3: RAG1 mediates signal sequence recognition and recruitment of RAG2 in V(D)J recombination. Difilippantonio MJ, McMahan CJ, Eastman QM, Spanopoulou E, Schatz DG; Cell. 1996;87:253-262. PMID:8861909

4: The RNase H-like superfamily: new members, comparative structural analysis and evolutionary classification. Majorek KA, Dunin-Horkawicz S, Steczkiewicz K, Muszewska A, Nowotny M, Ginalski K, Bujnicki JM; Nucleic Acids Res. 2014;42:4160-4179. PMID:24464998

5: Crystal structure of the V(D)J recombinase RAG1-RAG2. Kim MS, Lapkouski M, Yang W, Gellert M; Nature. 2015;518:507-511. PMID:25707801