Updated: August 20, 2013
Erin A. White
CBC Scholar: Class of 2010
PhD Candidate, Department of Molecular Genetics and Cell Biology (BSD), UChicago, Advisor: Michael Glotzer
GLOTZER LAB WEBPAGE
On February 14, 2013, Erin successfully defended her thesis: "CYK-4 binding induces a large scale conformational change in the kinesin subunit of the centralspindlin complex." Congratulations!
At anaphase onset, a set of overlapping, antiparallel, non-kinetochore microtubules become bundled forming the central spindle. This structure is essential for the completion of cytokinesis and can dictate the position of the division plane. Central spindle assembly is controlled by the concerted actions of microtubule associated proteins and kinesin family motor proteins, most notably centralspindlin. The centralspindlin heterotetramer is comprised of two molecules each of a kinesin-6 family motor protein, ZEN-4, and a Rho GTPase activating protein CYK-4. Through its accumulation on a narrow region of antiparallel microtubule overlap immediately following chromosome segregation, centralspindlin initiates central spindle assembly. Although it is known that microtubule bundling by centralspindlin requires a high-affinity interaction between ZEN-4 and CYK-4, the mechanism of action of CYK-4 in microtubule bundling is not clear. Intriguingly, CYK-4 binds ZEN-4 in the linker region between the motor domain and the coiled coil, a key region for motility of other kinesins. This raises the possibility that CYK-4 binding allosterically modifies the structural and/or biochemical properties of ZEN-4. To directly address whether CYK-4 binding induces conformational changes in the linker regions of ZEN-4, we used EPR spectroscopy. ZEN-4 molecules comprised of the minimal CYK-4 binding region and the coiled-coil were spin-labeled at specific positions and the distances between sites determined in the presence and absence of CYK-4. We found that CYK-4 binding induces a global structural rearrangement in ZEN-4 that results in a dramatic stabilization of the relative positions of the two linker regions. Our results also suggest that the linker region of ZEN-4 is likely to be structured in both the bound and unbound states. We are currently investigating whether CYK-4 binding alters the positions of the motor domains of ZEN-4, which could greatly impact the mechanism of motility of ZEN-4 in vivo.
White EA, Raghuraman H, Perozo E, Glotzer M. CYK-4 binding induces a large-scale conformational change in the kinesin subunit of the centralspindlin complex. J Biol Chem. 2013 Jul 5;288(27):19785-95. (PubMed)
White EA, Glotzer M. Centralspindlin: At the heart of cytokinesis. Cytoskeleton (Hoboken). 2012 Nov;69(11):882-92. (PubMed)
CBC Scholar, 2010-2011