Amino acid residues at the inter-subunit interface of a Cry4Aa monomer within the pre-pore trimer. (a) side view with Group 1's residues rendered as van der Waals (vdW) spheres and Group 2's residues rendered as sticks. Green is for polar and white is for non-polar. Blue is for positively charged and red is for negatively charged. One of Cry4Aa is depicted as surface and colored in spectrum from red to white to blue by residue number. The other two Cry4Aa monomers M2 and M3 are rendered as lines and colored red and green. (b) top view of (a), (c) Group 1's residues rendered as sticks, and (d) Group 2's residues depicted as sticks with Group 1's residues depicted as vdW spheres.