Figure 6.

Monomer-dimer transition state diagram. (A) The monomer-dimer interconversion is suggested to proceed via a transition state that loosely resembles either molecule of the dimer. As outlined in the text, the monomer stability is proposed to be slightly compromised by intrinsic structural features, particularly the lack of constraints on αB orientation and the truncation of αD. Loss of several N-terminal residues resulting from the inter-domain tug-of-war further destabilizes the monomer. (B) Overlaid ribbon diagrams for residues 427–506 (i.e. showing β1- β2- β3-αA-β4-αB) in the monomer (gray) and each molecule of the domain swapped dimer (green, yellow). The molecules were aligned from residues 427–495 to illustrate the variable positioning of helix αB.