Figure 5. General model for transition between alternative oligomeric states.

Transition from n-subunit to (n+1)-subunit state could be accomplished either by deletion (green triangles) at the outer side of the inter-subunit rotation axis (A) or insertion (light blue triangles) at the inner side of the axis (B). Inserts with three-dimensional representation show two adjacent subunits of each oligomer, with the intersubunit axis relating rotation of adjacent subunits during transition between the two states shown in yellow.