Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 283, Issue 4, Pages 2078-2087Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M708354200
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Funding
- NIAMS NIH HHS [K02 AR047841-05, K02 AR047841, K02-AR47841, K02 AR047841-04, K02 AR047841-03] Funding Source: Medline
- NIGMS NIH HHS [R01-GM54141, R01 GM054141-09, R01 GM054141-12, R01 GM054141-10, R01 GM054141, R01 GM054141-13, R01 GM054141-11, R01 GM054141-08] Funding Source: Medline
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Eg5/KSP is the kinesin-related motor protein that generates the major plus-end directed force for mitotic spindle assembly and dynamics. Recent work using a dimeric form of Eg5 has found it to be a processive motor; however, its mechanochemical cycle is different from that of conventional Kinesin-1. Dimeric Eg5 appears to undergo a conformational change shortly after collision with the microtubule that primes the motor for its characteristically short processive runs. To better understand this conformational change as well as head-head communication during processive stepping, equilibrium and transient kinetic approaches have been used. By contrast to the mechanism of Kinesin-1, microtubule association triggers ADP release from both motor domains of Eg5. One motor domain releases ADP rapidly, whereas ADP release from the other occurs after a slow conformational change at similar to 1 s(-1). Therefore, dimeric Eg5 begins its processive run with both motor domains associated with the microtubule and in the nucleotide-free state. During processive stepping however, ATP binding and potentially ATP hydrolysis signals rearward head advancement 16nm forward to the next microtubule-binding site. This alternating cycle of processive stepping is proposed to terminate after a few steps because the head-head communication does not sufficiently control the timing to prevent both motor domains from entering the ADP-bound state simultaneously.
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