"We have now identified the second step in how Bak forms that pore," Dr Kluck said. "Once the doublet is formed it can combine with other Bak doublets by what's called a second interface. This second interface seems to allow doublets to assemble into the larger complexes that form the pore."

The team of Dr Kluck, Dr Grant Dewson, Mr Tobias Kratina, Dr Peter Czabotar and Professor Jerry Adams from the institute and Dr Catherine Day from the University of Otago published their finding in the 25 November issue of Molecular Cell.

Dr Kluck said the team would continue to study how the large complexes of Bak and Bax force a hole in the mitochondrial membrane, how to start this process more effectively in cancer cells, and how to prevent it in brain and other healthy cells.

"A major black box in understanding apoptosis is how Bak and Bax work. Because these proteins change shape and lodge in a membrane they are hard to study. Any understanding we gain about how Bak and Bax form a pore, how they change shape and how they bind to each other, will help us understand how cancer cells can be targeted to die."