| Abstract No.: | 106 |
| Country: | Canada |
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| Title: | STRUCTURE, INTERACTIONS AND FOLDING OF PARKIN, AND E3 LIGASE IN AUTOSOMAL RECESSIVE PARKINSON'S DISEASE |
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| Authors/Affiliations: | 1 Gary S. Shaw*;
1 University of Western Ontario, London, ON, Canada
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| Content: | The central protein responsible for autosomal recessive juvenile parkinsonism (AR-JP) is the 465-residue enzyme Parkin (park2). This protein functions as an E3 ligase within the ubiquitin cascade used for protein degradation or in some cases, signaling. During this cascade parkin has been shown to utilize the E2 conjugating enzymes UbcH7 and UbcH8 in order to transfer the small modifier protein ubiquitin to substrates targeted for degradation by the proteasome. It is well established that single site mutations in parkin can lead to a disruption of its function. However, the role mutations have in AR-JP is not currently understood.
Parkin is a complex modular protein comprising an N-terminal 76-residue “ubiquitin-like” domain (UbLD) and two C-terminal RING domains (RING1, RING2) separated by an In-Between RING domain (IBR). We have examined the structure and function of parkin and the role mutations have in its interactions with the S5a subunit of the proteasome. Using nuclear magnetic resonance spectroscopy we have determined the structure of the parkin IBR domain and shown this domain possesses two novel zinc-binding motifs. Zinc binding to the IBR domain is required to maintain its three-dimensional structure indicating that zinc is an important co-factor in parkin function. Further, single-site mutations associated with AR-JP within the IBR domain have different affects on the protein structure causing either unfolding of the domain or disrupting protein-protein interactions. We have also used a variety of biophysical methods to determine how parkin interacts with the S5a subunit of the proteasome, thought to be important for delivering ubiquitinated proteins for degradation. Our work shows that parkin recognizes specific regions of the S5a subunit and that the parkin-S5a interaction is disrupted by AR-JP causing mutations.
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