Shown in A is a map of AAV2 X homologies against the full length Rep78 protein. However, for Go.1, related to AAV5, the homology resides at the extreme carboxy-terminus of Rep78, different from the other AAVs. B, C, and D are NCBI Protein BLAST homology analyses between AAV2 X and AAV type 2, 4, 8, and Go.1 Rep78/NS1 proteins. Note that for most Rep78s the homology with X lies in a region from 100–200 aa. These homologies suggest that Rep78 DNA sequences may have exchanged material with the 3′ end of the AAV genomes. AAV8 may be the most likely source due to its longest length of homology. The putative DNA/RNA binding domain of X and the RCR3 domain of Rep78 are marked.