Figure 7

Mutations that cause elongated ovoid focus assembly. A. Single alanine substitution mutations for Ser398, Glu416 and Arg462 caused the TnaA-sfGFP variants to form elongated ovoid foci. The GFP images are overlaid with phase contrast images. B. The three residues (green) are mapped to the bottom of the loop (purple) at edge of catalytic pocket (yellow), on the crystal structures in the open (PDB 2OQX) and closed conformation (PDB 2C44) of TnaA. The structures are in side view compared to the structure in Figure 3A, with the same color codes. Only the upper catalytic pocket is highlighted. C. Ser398, Glu416 and Arg462 may form hydrogen bonds to stabilize the loop. Cartoon views of TnaA residues 398–462, with Ser398, Glu416 and Arg462 are illustrated in stick form. Nitrogen atoms (blue) and oxygen atoms (red) are marked. Possible hydrogen bonds between the three residues are illustrated, with distances indicated in Å.