The Structural Basis of Force Generation by the Mitotic Motor Kinesin-5

• Published in: The Journal of biological chemistry 2012-12, Vol.287 (53), p.44654-44666
• Main Authors: Goulet, Adeline, Behnke-Parks, William M., Sindelar, Charles V., Major, Jennifer, Rosenfeld, Steven S., Moores, Carolyn A.
• Format: Article
• Language: English
• Subjects: Binding Sites; Cryoelectron Microscopy; Fluorescence; Humans; Kinesin; Kinesin - chemistry; Kinesin - genetics; Kinesin - metabolism; Kinetics; Life Sciences; Microtubules; Microtubules - genetics; Microtubules - metabolism; Mitosis; Models, Molecular; Molecular Motors; Nucleotides - metabolism; Protein Binding; Protein Conformation; Protein Structure and Folding; Protein Structure, Tertiary; Spindle Apparatus - chemistry; Spindle Apparatus - metabolism; Structural Biology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.404228

Kinesin-5 is required for forming the bipolar spindle during mitosis. Its motor domain, which contains nucleotide and microtubule binding sites and mechanical elements to generate force, has evolved distinct properties for its spindle-based functions. In this study, we report subnanometer resolution cryoelectron microscopy reconstructions of microtubule-bound human kinesin-5 before and after nucleotide binding and combine this information with studies of the kinetics of nucleotide-induced neck linker and cover strand movement. These studies reveal coupled, nucleotide-dependent conformational changes that explain many of this motor's properties. We find that ATP binding induces a ratchet-like docking of the neck linker and simultaneous, parallel docking of the N-terminal cover strand. Loop L5, the binding site for allosteric inhibitors of kinesin-5, also undergoes a dramatic reorientation when ATP binds, suggesting that it is directly involved in controlling nucleotide binding. Our structures indicate that allosteric inhibitors of human kinesin-5, which are being developed as anti-cancer therapeutics, bind to a motor conformation that occurs in the course of normal function. However, due to evolutionarily defined sequence variations in L5, this conformation is not adopted by invertebrate kinesin-5s, explaining their resistance to drug inhibition. Together, our data reveal the precision with which the molecular mechanism of kinesin-5 motors has evolved for force generation. Kinesin-5 motors are important for formation and maintenance of the bipolar mitotic spindle. ATP binding triggers coupled conformational changes of kinesin-5 specific structural elements in the microtubule-bound motor domain. Kinesin-5 mechanochemistry is tuned to its cellular functions. Subnanometer resolution structure determination of microtubule-bound kinesin-5s and kinetics experiments reveal the molecular basis of their motor properties and of drug inhibition.