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. Author manuscript; available in PMC: 2017 May 17.
Published in final edited form as: Biochemistry. 2016 May 3;55(19):2748–2759. doi: 10.1021/acs.biochem.6b00167

Figure 4.

Figure 4

Crystal structure of apo ToxA. (A) Apo ToxA forms a homodimer having noncrystallographic twofold symmetry. (B) Homotetramic arrangement of apo ToxA observed within the crystal packing. Two dimers having the structure shown in panel A form a homotetramer with 222 symmetry. (C) A flexible loop (Val180-Thr181-Asp182-Pro183-Pro184) from the adjacent chain inserts into the azapteridine binding site and prevents the N-terminal segment from folding over the active site. 1,6-DDMT and SAH are superimposed onto the apo structure to indicate potential steric clashes.