AAA+ ATPases are involved in a wide array of critical cellular events in all kingdoms of life and frequently rely on adaptor proteins to modulate substrate specificity. CIpX is an AAA+ ATPase that unfolds protein substrates and translocates them into the proteolytic chamber of CIpP for degradation. The delivery protein SspB dramatically enhances the CIpXP degradation of proteins with a specific C-terminal peptide sequence called the ssrA-tag. SspB is a homodimer that binds two ssrA-tagged substrates and presents them to CIpXP for degradation. Our current view is that SspB is loosely tethered to CIpX by flexible C-terminal linkers that end with a CIpX binding (XB) sequence, allowing it to sequentially deliver both substrate molecules for degradation. However, it is not known whether the SspB dimer comes apart during the delivery process, whether both substrates are in fact delivered, whether both XB regions in the dimer are critical for interactions with CIpX, or whether SspB can function as a monomer. I propose to answer these questions by using mutant proteins defective in specific properties together with biochemical and biophysical assays to test and refine our model for how this fascinating biological system works. The studies proposed herein will define the role of dimerization in SspB function. In addition to CIpX, many other members of the AAA+ ATPases interact with oligomeric adapter proteins including SNARE/NSF. Understanding the role of SspB dimerization in its function with CIpXP could broadly impact our understanding of the interactions of other oligomeric adapters with AAA+ ATPases.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
1F32GM070231-01
Application #
6739176
Study Section
Special Emphasis Panel (ZRG1-F04 (20))
Program Officer
Basavappa, Ravi
Project Start
2004-01-01
Project End
2005-12-31
Budget Start
2004-01-01
Budget End
2004-12-31
Support Year
1
Fiscal Year
2004
Total Cost
$42,976
Indirect Cost
Name
Massachusetts Institute of Technology
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
001425594
City
Cambridge
State
MA
Country
United States
Zip Code
02139