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Rayment Lab - When is a motor not a motor?
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A Kinesin Motor without a Nucleotide Binding Site
It is widely accepted that kinesin molecular motors contain a motor
domain that hydrolyzes ATP and through a series of nucleotide-dependent
conformational changes translate the free energy of hydrolysis into
directed movement. Thus it comes as a complete surprise that the
kinesin related protein Vik1 contains a motor domain, but does not
include an active site. This non-motor polypeptide heterodimerizes with
the kinesin Kar3. Surprisingly, Vik1 can bind tightly to microtubules
independently of Kar3, but still permits movement of Kar3 along
microtubules. These traits demand that there is communication between
Kar3 and Vik1, perhaps through a novel strain-dependent mechanism, that
allows the binding affinity of Vik1 for microtubules to be modulated by
the nucleotide state of Kar3. From an evolutionary viewpoint it is
appears that Vik1 evolved from a primordial gene belonging to the same
kinesin family as Kar3. Remarkably, the ability to bind and hydrolyze
nucleotide was lost during evolution, but the ability to interact with
microtubules and communicate with its associated motor protein Kar3 was
retained. These studies suggest new variations of molecular motor
interactions await discovery.
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Learn more about research by Ivan Rayment
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