Simulation of conformational changes in 2 Zn insulin.

Isolated insulin monomers, the dimer and higher aggregates from the 2 Zn crystal structure are subjected to convergent energy minimization in Cartesian co-ordinates using a force-field that includes the position of all hydrogen atoms. The minimizations are found, for the first time, to produce conformational changes of appreciable magnitude, which agree well with observed structural differences between monomers in the 2 Zn crystal and with the mechanism proposed previously for the coupling between deformations in different parts of the molecule. Our results also suggest that insulin would tend to adopt a molecule 1-like conformation in the absence of crystal packing forces, and that dimer formation is not at the origin of the observed asymmetry in the 2 Zn crystal.