CRYSTALLOGRAPHic studies of the mitochondrial fission protein fis1

 

Michael A. Gorman,a Diana Stojanovski,b Michael T.Ryan b and Jacqueline M. Gulbis a

 

aDepartment of Structural Biology, The Walter and Eliza Hall Institute, 1G Royal Parade, Parkville, Victoria, 3050, Australia;  bDepartment of Biochemistry, La Trobe  University, Victoria, 3086, Australia (gorman@wehi.edu.au).

 

 

The vital role of mitochondria for ATP production, Ca2+ homeostasis and initiation of apoptosis has been apparent for some time. Mitochondria are not singular organelles but are dynamic structures that divide and fuse continually throughout the life of the cell. Since mitochondria are not created de novo, they must proliferate and segregate into daughter cells during cell division so that each one maintains a full complement. Most of the work has been done in the model system of S. cerevisiae in which two conserved GTPases regulate mitochondrial shape. Fzo1p[1] mediate mitochondrial fusion and Dnm1p[2] regulates mitochondrial fission. Loss of Dnm1p function impairs fission resulting in the formation of highly connected networks due to the accumulation of unopposed fusion events. In yeast, two additional proteins Mdv1p and Fis1p are essential components of the fission machinery[3]. Fis1p is an integral mitochondrial outer membrane protein recruiting Dnm1p and Mdv1p to the surface of the outer membrane. In vivo studies indicate the intact C-terminal structure of Fis1p is essential for localisation whereas the N-terminal region of Fis1p is necessary for mitochondrial fission. In mammalian cells, the dynamin-like homologue to Dnm1p, Drp1p, is also required for mitochondrial fission. It is distributed predominantly in the cytosol and is transiently associated with mitochondria. The human homologue hFis1 shares 25% sequence identity and 61% sequence similarity with the yeast counterpart. The structures of hFis1 and hFis1/Drp1p complex will help identify the molecular interaction and how specificity is achieved. To this aim, the cytosolic domain of hFis1 has been expressed as a GST-fusion protein and the progress towards the determination of hFis1p X-ray crystal structure will be discussed.

 

References

1       Rapaport, D., Brunner, M., Neupert, W. and Westermann (1998) J. Cell. Biol. 273, 20150-20155.

2       Otsuga,D. et al (1998) J. Cell. Biol.  143, 333-349.

3       A.D.Mozdy,J.M.McCaffery and J.M.Shaw (2000) J. Cell. Biol. 151, 376-379.