Opening image: Crystal structure of the asymmetrical cpn60-cpn10-ADP complex from E. coli. The seven ADP molecules are shown in magenta.
The bullet complex consist of three rings stacked on top of each other. In the case of cpn60, the stack back to back. This double ring structure is stabilized by interactions between the domains of each cpn60 subunit. Each ring encloses a large central cavity. The two cavities alternate between two conformations. Seven ADP molecules are bound to the 'open' ring.