Crystal structure and structure-based mutagenesis of actin-specific ADP-ribosylating toxin CPILE-a as novel enterotoxin
Fig 3
Structure comparison with apo-CPILE-a, NAD+-CPILE-a, NADH-CPILE-a and close-up view of NAD-binding site of CPILE-a, Ia and BECa.
A, Superimposed structures of NAD+-CPILE-a and apo-CPILE-a indicated that the binding to NAD+ did not induce conformational change to CPILE-a. The N-terminal domain and the C-terminal domain of NAD+-CPILE-a are shown in marine and yellow, respectively. The apo-CPILE-a is shown in orange. B, Superimposed structures of NAD+-CPILE-a and NADH-CPILE-a (lime green) showed very similar structure with r.m.s.d. 0.23 (Å). C, Superimposed structures of NAD+-CPILE-a and Ia (4H03). Ia and actin showed in white and green, respectively. D, Stereo-view of NAD+-CPILE-a (yellow) and NAD+-Ia (4H03) focused on ligand-binding site (NAD+). Ten residues represent the close-contact residues to the NAD+. All residues labeled here belong to the NAD+-CPILE-a. E, Stereo-view of the 2Fo-Fc electron density map of the NAD+ contoured at 2σ. F, Superimposed structure of NADH-CPILE-a, apo-BEC-a (5H03), and NADH-BECa (5H04) focused on ligand binding site. A distinct residue (Tyr377) on the ARTT-loop is shown in stick model. The NAD+-CPILE-a, NADH-CPILE-a, apo-BECa, and NADH-BECa are shown in yellow, green, tint, and split pea, respectively.