BIOL 429 DISC 2

BIOL 429 DISC 2 - B i ol og y 4 2 9 Pa per 2 N otes for...

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Biology 429 Paper 2 – Notes for Discussion Section Wednesday, September 22, 2010 Masato, Y., K. Terada, M. Masataka. 2004. Mitochondrial Import Receptors Tom20 and Tom22 Have Chapterone-like Activity. Journal of Biological Chemistry 279: 10808-10813. Discussion - The importance of cytosolic chaperones has been previously established (1-3) - Prior to this study, there were few (if any) studies on chaperone functions of mitochondrial surface proteins - This study shows that Tom20, which is a mitochondrial surface protein, binds to unfolded proteins regardless of the presence or absence of presequence amino acids Suggests that Tom20 functions as a receptor for both proteins with presequences as well as unfolded proteins that have no presequences. A number of mitochondrial proteins are known to be transported through the cytosol in an unfolded state However it has not been known to what extent the unfolded state is maintained on the way to the mitochondrial surface The authors seem to say some contradictory things here: Some preproteins are in a folded state upon their arrival at the mitochondrial surface, and are pulled through the pore in an unfolded state by the Hsp70 molecule This study suggests that some mitochondrial proteins are maintained in an unfolded state all the way to the mitochondrial surface ALSO, this study suggests that Tom20 and Tom22 serve as receptors for the partially unfolded portions of preproteins - Tom20 also demonstrates chaperone-like activity capable of suppressing the thermal aggregation of mitochondrial proteins May be important to suppress aggregation, maintaining mitochondria-targeted
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BIOL 429 DISC 2 - B i ol og y 4 2 9 Pa per 2 N otes for...

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