November 24, 2015 10:00 - 11:00
In axons, ATP-hydrolyzing motor proteins such as kinesin and dynein transport cargo along microtubule (MT) tracks. In this mechanism, MTs have been considered to be passive tracks for motor proteins. However, our early observations with in vitro motility assays showed that kinesin-coated latex beads bind to a MT in a cooperative manner, and the cooperativity was observed only in the presence of ATP. This indicates that MTs may dynamically change their conformation during the motility of kinesin and be involved in the motor's ATPase cycle.
To investigate how a MT is involved in the motor’s ATPase cycle, we conducted extensive mutational analysis of tubulin, a technique unique to our lab. We found that both kinesin and dynein use precisely the same loop/helix in α-tubulin to activate their ATPases, despite the fact that these motors belong to different enzyme classes and are in different subdomain organizations. The results indicate that the ATPase-activating function of this loop/helix leads to a convergent evolution of two motors. Furthermore, a comparison of the reported structures of a TOG:αβ-tubulin complex and a kinesin:αβ-tubulin complex has led us to propose that this loop/helix serves as a switch to induce a partially-bent conformation in tubulin.
Motility and structure analyses are now in progress using multiple new lines of mutant MTs. In these mutants, the equilibrium among multiple conformations is biased to a specific one. We hope to identify the putative dynamic changes in MTs induced by motors and to unveil the allosteric regulation of motility by MTs.
- BSI Private Event
- Hiroyuki Kamiguchi [Hiroyuki Kamiguchi, Neuronal Growth Mechanisms ]