Speaker
Mr
Angus Cowan
(The Walter and Eliza Hall Institute)
Description
The Bcl-2 protein family regulates the intrinsic apoptotic pathway and the critical step of mitochondrial outer membrane permeabilisation (MOMP). MOMP results in the release of Cytochrome *c* and other molecules from the intermembrane space, leading to the formation of the apoptosome and caspase activation. Bax and Bak are structurally and functionally homologous pro-apoptotic Bcl-2 proteins that facilitate MOMP. BH3-only proteins such as Bim transiently bind to and activate Bax and/or Bak resulting in their homodimerisation and oligomerisation. The large Bax/Bak oligomers disrupt the mitochondrial outer membrane causing MOMP. BH3-only protein binding causes the dissociation of Bax/Bak into two distinct domains known as the "core" and "latch" domains. The structures of both homodimerised Bax and homodimerised Bak core domains, with a GFP fusion tag to aid crystallisation, have been solved. The core domains dimerise through a symmetrical interface involving the reciprocal insertion of the BH3 domain alpha helix of one Bax/Bak molecule into the hydrophobic groove of the partner Bax/Bak molecule. To further investigate the Bax core domain, we have expressed it as a GST fusion protein and removed the GST tag. The cleaved core domain remains soluble and runs as a multimer (likely a hexamer or an octamer) on a size exclusion column. The structure of this multimer could provide insight into the nature of the large Bax oligomers that have remained structurally enigmatic despite decades of investigation.
| Keywords | Apoptosis Bcl-2 Bax Bak |
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Primary author
Mr
Angus Cowan
(The Walter and Eliza Hall Institute)
Co-authors
Prof.
Peter Colman
(Walter and Eliza Hall Institute)
Dr
Peter Czabotar
(Walter and Eliza Hall Institute)
