Getting in sync with dimeric Eg5. Initiation and regulation of the processive run.
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 approximately 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 16 nm 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.
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
Troy C
TC
Krzysiak
Michael
M
Grabe
Susan P
SP
Gilbert
D000244:Adenosine Diphosphate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D006801:Humans; D006868:Hydrolysis; D016547:Kinesins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020836:Protein Structure, Quaternary / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014404:Tubulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
C470243:KIF11 protein, human; D011994:Recombinant Proteins; D014404:Tubulin; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D016547:Kinesins