The B. anthracis nrdE intron encodes a GIY-YIG HEase. (A) I-BanI, identified as a GIY-YIG endonuclease, contains an N-terminal GIY-YIG domain (red box) with the GIY-YIG endonuclease motif, a C-terminal GIY-YIG domain (blue box) with a minor-groove DNA binding α-helix motif, and a helix-turn-helix motif (yellow box). A large deletion in I-BthI spans most of both the N-terminal and C-terminal domains. (B) [35S]Met-radiolabeled in vitro translation of I-BthI and I-BanI showed products of 5 kDa and 30 kDa, respectively.