Identification of two catalytic residues in RAG1 that define a single active site within the RAG1/RAG2 protein complex

During V(D)J recombination, the RAG1 and RAG2 proteins cooperate to catalyz e a series of DNA bond breakage and strand transfer reactions. The structur e, location, and number of active sites involved in RAG-mediated catalysis have as yet not been determined. Using protein secondary structure predicti on algorithms, we have identified a region of RAG1 with possible structural similarities to the active site regions of transposases and retroviral int egrases. Based on this information, we have identified two aspartic acid re sidues in RAG1 (D600 and D708) that function specifically in catalysis. The results support a model in which RAG1 contains a single, divalent metal io n binding active site structurally related to the active sites of transposa ses/integrases and responsible for all catalytic functions of the RAG prote in complex.