Intersubunit contacts between NCT LL and PS1 HL1 facilitated by the global bending mode. (A) Initial structure of the complex (PDB: 5FN2). (B) Closed form enabled by ANM mode 1, based on an RMSD of 4 Å from the initial structure. Q540, D541, R543, R583, E584, P593, and S611 in NCT, and Y106, R108-D110, Y115, and E120–E123 in PS1 are shown as red (negatively charged), blue (positively charged), or orange (polar) sticks. We note a cluster of interactions involving D121–E123 on HL1 and Q540–R543 at the NCT LL surface groove mouth (encircled). See also Movie S1 and Table S1 for close intersubunit interactions in the closed form favored by mode 1.