Neck-Linker Length Dependence of Processive Kinesin-5 Motility
ABSTRACT Processive motility of individual molecules is essential for the function of many kinesin motors. Processivity for kinesins relies on communication between the two heads of a dimeric molecule, such that binding strictly alternates. The main communicating elements are believed to be the two neck linkers connecting the motors' stalks and heads. A proposed mechanism for coordination is the transmission of stress through the neck linkers. It is believed that the efficiency of gating depends on the length of the neck linker. Recent studies have presented support for a simple model in which the length of the neck linker directly controls the degree of processivity. Based on a previously published Kinesin-1/Kinesin-5 chimera, Eg5Kin, we have analyzed the motility of 12 motor constructs: we have varied the length of the neck linker in the range between 9 and 21 amino acids using the corresponding native Kinesin-5 sequence (Xenopus laevis Eg5). We found, surprisingly, that neither velocity nor force generation depended on neck-linker length. We also found that constructs with short neck linkers, down to 12 amino acids, were still highly processive, while processivity was lost at a length of 9 amino acids. Run lengths were maximal with neck linkers close to the native Kinesin-5 length and decreased beyond that length. This finding generally confirms the coordinating role of the neck linker for kinesin motility but challenges the simplest model postulating a motor-type-independent optimal length. Instead, our results suggest that different kinesins might be optimized for different neck-linker lengths.
- SourceAvailable from: onlinelibrary.wiley.com[Show abstract] [Hide abstract]
ABSTRACT: Mitotic cell division is the most fundamental task of all living cells. Cells have intricate and tightly regulated machinery to ensure that mitosis occurs with appropriate frequency and high fidelity. A core element of this machinery is the kinesin-5 motor protein, which plays essential roles in spindle formation and maintenance. In this review, we discuss how the structural and mechanical properties of kinesin-5 motors uniquely suit them to their mitotic role. We describe some of the small molecule inhibitors and regulatory proteins that act on kinesin-5, and discuss how these regulators may influence the process of cell division. Finally, we touch on some more recently described functions of kinesin-5 motors in non-dividing cells. Throughout, we highlight a number of open questions that impede our understanding of both this motor's function and the potential utility of kinesin-5 inhibitors. This article is protected by copyright. All rights reserved.Biology of the Cell 10/2013; 106(1). DOI:10.1111/boc.201300054 · 3.87 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Kinesin5 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 kinesin5 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 amino-terminal cover strand. Loop L5-the binding site for allosteric inhibitors of kinesin5-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 kinesin5, 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 kinesin5s, explaining their resistance to drug inhibition. Together, our data reveal the precision with which the molecular mechanism of kinesin5 motors has evolved for force generation.Journal of Biological Chemistry 11/2012; 104(2). DOI:10.1074/jbc.M112.404228 · 4.60 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Kinesin-5 motors are members of a superfamily of microtubule-dependent ATPases and are widely conserved among eukaryotes. Kinesin-5s typically form homotetramers with pairs of motor domains located at either end of a dumbbell-shaped molecule. This quaternary structure enables cross-linking and ATP-driven sliding of pairs of microtubules, although the exact molecular mechanism of this activity is still unclear. Kinesin-5 function has been characterized in greatest detail in cell division, although a number of interphase roles have also been defined. The kinesin-5 ATPase is tuned for slow microtubule sliding rather than cellular transport and-in vertebrates-can be inhibited specifically by allosteric small molecules currently in cancer clinical trials. The biophysical and structural basis of kinesin-5 mechanochemistry is being elucidated and has provided further insight into kinesin-5 activities. However, it is likely that the precise mechanism of these important motors has evolved according to functional context and regulation in individual organisms.International review of cell and molecular biology 01/2013; 304C:419-466. DOI:10.1016/B978-0-12-407696-9.00008-7 · 4.52 Impact Factor