Fig. 1.

Crystal structure of GNIP1Aa in ribbon representation. The figure was made with PyMOL (33). (A) The structure of GNIP1Aa is composed of two domains. The N-terminal MACPF domain is colored green with key structural features shown in different colors: central four-stranded β-sheet in purple; two clusters of helices, CH1 and CH2, in cyan; and MACPF-conserved α-helix in yellow. Additionally, the signature MACPF motif and two conserved glycines are highlighted in orange and red, ¹⁶⁷YGPYYX₆GG¹⁷⁹ and ²⁴⁰GG²⁴¹, respectively. The linker between the two domains is shown in black. The C-terminal domain is colored light blue with an exception of three apical loops in magenta and the C-terminal tail in pink. (B) Close-up of the conserved MACPF residues, ¹⁶⁷YGPYYX₆GG¹⁷⁹ and ²⁴⁰GG²⁴¹, shown in stick presentation in orange and red, respectively. (C) Superposition of GNIP1Aa structure in yellow with bacterial MACPF protein from P. luminescens (PDB ID code 2QP2) in blue; RMSD of 2.3 Å for 298 Cα positions. (D) Superposition of GNIP1Aa structure in yellow with a representative of CDCs, perfringolysin O (PDB ID code 1M3I) in red; RMSD of 4.1 Å for 209 Cα positions.