1
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Hunter B, Allingham JS. These motors were made for walking. Protein Sci 2020; 29:1707-1723. [PMID: 32472639 DOI: 10.1002/pro.3895] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 05/19/2020] [Accepted: 05/22/2020] [Indexed: 12/21/2022]
Abstract
Kinesins are a diverse group of adenosine triphosphate (ATP)-dependent motor proteins that transport cargos along microtubules (MTs) and change the organization of MT networks. Shared among all kinesins is a ~40 kDa motor domain that has evolved an impressive assortment of motility and MT remodeling mechanisms as a result of subtle tweaks and edits within its sequence. Several elegant studies of different kinesin isoforms have exposed the purpose of structural changes in the motor domain as it engages and leaves the MT. However, few studies have compared the sequences and MT contacts of these kinesins systematically. Along with clever strategies to trap kinesin-tubulin complexes for X-ray crystallography, new advancements in cryo-electron microscopy have produced a burst of high-resolution structures that show kinesin-MT interfaces more precisely than ever. This review considers the MT interactions of kinesin subfamilies that exhibit significant differences in speed, processivity, and MT remodeling activity. We show how their sequence variations relate to their tubulin footprint and, in turn, how this explains the molecular activities of previously characterized mutants. As more high-resolution structures become available, this type of assessment will quicken the pace toward establishing each kinesin's design-function relationship.
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Affiliation(s)
- Byron Hunter
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - John S Allingham
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
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2
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Ziemianowicz DS, MacCallum JL, Schriemer DC. Correlation between Labeling Yield and Surface Accessibility in Covalent Labeling Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:207-216. [PMID: 32031402 DOI: 10.1021/jasms.9b00083] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The functional properties of a protein are strongly influenced by its topography, or the solvent-facing contour map of its surface. Together with crosslinking, covalent labeling mass spectrometry (CL-MS) has the potential to contribute topographical data through the measurement of surface accessibility. However, recent efforts to correlate measures of surface accessibility with labeling yield have been met with mixed success. Most applications of CL-MS involve differential analysis of protein interactions (i.e., footprinting experiments) where such inconsistencies have limited effect. Extending CL-MS into structural analysis requires an improved evaluation of the relationship between labeling and surface exposure. In this study, we applied recently developed diazirine reagents to obtain deep coverage of the large motor domain of Eg5 (a mitotic kinesin), and together with computational methods we correlated labeling yields with accessibility data in a number of ways. We observe that correlations can indeed be seen at a local structural level, but these correlations do not extend across the structure. The lack of correlation arises from the influence of protein dynamics and chemical composition on reagent partitioning and, thus, also on labeling yield. We conclude that our use of CL-MS data should be considered in light of "chemical accessibility" rather than "solvent accessibility" and suggest that CL-MS data would be a useful tool in the fundamental study of protein-solute interactions.
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Affiliation(s)
- Daniel S Ziemianowicz
- Department of Biochemistry and Molecular Biology , University of Calgary , Calgary , Alberta , Canada T2N 4N1
- Robson DNA Science Centre, Arnie Charbonneau Cancer Institute , University of Calgary , Calgary , Alberta , Canada T2N 4N1
| | - Justin L MacCallum
- Department of Chemistry , University of Calgary , Calgary , Alberta , Canada T2N 4N1
| | - David C Schriemer
- Department of Biochemistry and Molecular Biology , University of Calgary , Calgary , Alberta , Canada T2N 4N1
- Robson DNA Science Centre, Arnie Charbonneau Cancer Institute , University of Calgary , Calgary , Alberta , Canada T2N 4N1
- Department of Chemistry , University of Calgary , Calgary , Alberta , Canada T2N 4N1
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3
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Kim CD, Kim ED, Liu L, Buckley RS, Parameswaran S, Kim S, Wojcik EJ. Small molecule allosteric uncoupling of microtubule depolymerase activity from motility in human Kinesin-5 during mitotic spindle assembly. Sci Rep 2019; 9:19900. [PMID: 31882607 PMCID: PMC6934681 DOI: 10.1038/s41598-019-56173-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 12/06/2019] [Indexed: 01/22/2023] Open
Abstract
Human Kinesin-5 (Eg5) has a large number of known allosteric inhibitors that disrupt its mitotic function. Small-molecule inhibitors of Eg5 are candidate anti-cancer agents and important probes for understanding the cellular function. Here we show that Eg5 is capable of more than one type of microtubule interaction, and these activities can be controlled by allosteric agents. While both monastrol and S-trityl-L-cysteine inhibit Eg5 motility, our data reveal an unexpected ability of these loop5 targeting inhibitors to differentially control a novel Eg5 microtubule depolymerizing activity. Remarkably, small molecule loop5 effectors are able to independently modulate discrete functional interactions between the motor and microtubule track. We establish that motility can be uncoupled from the microtubule depolymerase activity and argue that loop5-targeting inhibitors of Kinesin-5 should not all be considered functionally synonymous. Also, the depolymerizing activity of the motor does not contribute to the genesis of monopolar spindles during allosteric inhibition of motility, but instead reveals a new function. We propose that, in addition to its canonical role in participating in the construction of the three-dimensional mitotic spindle structure, Eg5 also plays a distinct role in regulating the dynamics of individual microtubules, and thereby impacts the density of the mitotic spindle.
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Affiliation(s)
- Catherine D Kim
- Department of Biochemistry and Molecular Biology, LSU School of Medicine & Health Sciences Center, 1901 Perdido Street, New Orleans, LA, 70112, USA
| | - Elizabeth D Kim
- Department of Biochemistry and Molecular Biology, LSU School of Medicine & Health Sciences Center, 1901 Perdido Street, New Orleans, LA, 70112, USA
| | - Liqiong Liu
- Department of Biochemistry and Molecular Biology, LSU School of Medicine & Health Sciences Center, 1901 Perdido Street, New Orleans, LA, 70112, USA
| | - Rebecca S Buckley
- Department of Biochemistry and Molecular Biology, LSU School of Medicine & Health Sciences Center, 1901 Perdido Street, New Orleans, LA, 70112, USA
| | - Sreeja Parameswaran
- Department of Biochemistry and Molecular Biology, LSU School of Medicine & Health Sciences Center, 1901 Perdido Street, New Orleans, LA, 70112, USA
| | - Sunyoung Kim
- Department of Biochemistry and Molecular Biology, LSU School of Medicine & Health Sciences Center, 1901 Perdido Street, New Orleans, LA, 70112, USA
| | - Edward J Wojcik
- Department of Biochemistry and Molecular Biology, LSU School of Medicine & Health Sciences Center, 1901 Perdido Street, New Orleans, LA, 70112, USA.
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4
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Roostalu J, Rickman J, Thomas C, Nédélec F, Surrey T. Determinants of Polar versus Nematic Organization in Networks of Dynamic Microtubules and Mitotic Motors. Cell 2018; 175:796-808.e14. [PMID: 30340043 PMCID: PMC6198040 DOI: 10.1016/j.cell.2018.09.029] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 06/25/2018] [Accepted: 09/13/2018] [Indexed: 11/03/2022]
Abstract
During cell division, mitotic motors organize microtubules in the bipolar spindle into either polar arrays at the spindle poles or a "nematic" network of aligned microtubules at the spindle center. The reasons for the distinct self-organizing capacities of dynamic microtubules and different motors are not understood. Using in vitro reconstitution experiments and computer simulations, we show that the human mitotic motors kinesin-5 KIF11 and kinesin-14 HSET, despite opposite directionalities, can both organize dynamic microtubules into either polar or nematic networks. We show that in addition to the motor properties the natural asymmetry between microtubule plus- and minus-end growth critically contributes to the organizational potential of the motors. We identify two control parameters that capture system composition and kinetic properties and predict the outcome of microtubule network organization. These results elucidate a fundamental design principle of spindle bipolarity and establish general rules for active filament network organization.
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Affiliation(s)
| | - Jamie Rickman
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Claire Thomas
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - François Nédélec
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
| | - Thomas Surrey
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
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5
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De Rossi MC, Wetzler DE, Benseñor L, De Rossi ME, Sued M, Rodríguez D, Gelfand V, Bruno L, Levi V. Mechanical coupling of microtubule-dependent motor teams during peroxisome transport in Drosophila S2 cells. Biochim Biophys Acta Gen Subj 2017; 1861:3178-3189. [PMID: 28935608 DOI: 10.1016/j.bbagen.2017.09.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 09/04/2017] [Accepted: 09/15/2017] [Indexed: 12/24/2022]
Abstract
BACKGROUND Intracellular transport requires molecular motors that step along cytoskeletal filaments actively dragging cargoes through the crowded cytoplasm. Here, we explore the interplay of the opposed polarity motors kinesin-1 and cytoplasmic dynein during peroxisome transport along microtubules in Drosophila S2 cells. METHODS We used single particle tracking with nanometer accuracy and millisecond time resolution to extract quantitative information on the bidirectional motion of organelles. The transport performance was studied in cells expressing a slow chimeric plus-end directed motor or the kinesin heavy chain. We also analyzed the influence of peroxisomes membrane fluidity in methyl-β-ciclodextrin treated cells. The experimental data was also confronted with numerical simulations of two well-established tug of war scenarios. RESULTS AND CONCLUSIONS The velocity distributions of retrograde and anterograde peroxisomes showed a multimodal pattern suggesting that multiple motor teams drive transport in either direction. The chimeric motors interfered with the performance of anterograde transport and also reduced the speed of the slowest retrograde team. In addition, increasing the fluidity of peroxisomes membrane decreased the speed of the slowest anterograde and retrograde teams. GENERAL SIGNIFICANCE Our results support the existence of a crosstalk between opposed-polarity motor teams. Moreover, the slowest teams seem to mechanically communicate with each other through the membrane to trigger transport.
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Affiliation(s)
- María Cecilia De Rossi
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Biológica, Laboratorio de Dinámica Intracelular, Buenos Aires, Argentina; CONICET-Universidad de Buenos Aires, Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN), Buenos Aires, Argentina
| | - Diana E Wetzler
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Biológica, Laboratorio de Dinámica Intracelular, Buenos Aires, Argentina; CONICET-Universidad de Buenos Aires, Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN), Buenos Aires, Argentina
| | - Lorena Benseñor
- Fundación Instituto Leloir, CONICET, Buenos Aires, Argentina
| | - María Emilia De Rossi
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales y Ciclo Básico Común, Buenos Aires, Argentina; CONICET-Universidad de Buenos Aires, Instituto de Astronomía y Física del Espacio (IAFE), Buenos Aires, Argentina
| | - Mariela Sued
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Instituto de Cálculo, Buenos Aires, Argentina
| | - Daniela Rodríguez
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Instituto de Cálculo, Buenos Aires, Argentina
| | - Vladimir Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Luciana Bruno
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Física, Buenos Aires, Argentina; CONICET-Universidad de Buenos Aires, Instituto de Física de Buenos Aires (IFIBA), Buenos Aires, Argentina.
| | - Valeria Levi
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Biológica, Laboratorio de Dinámica Intracelular, Buenos Aires, Argentina; CONICET-Universidad de Buenos Aires, Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN), Buenos Aires, Argentina.
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6
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Bell KM, Cha HK, Sindelar CV, Cochran JC. The yeast kinesin-5 Cin8 interacts with the microtubule in a noncanonical manner. J Biol Chem 2017; 292:14680-14694. [PMID: 28701465 PMCID: PMC5582858 DOI: 10.1074/jbc.m117.797662] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 06/28/2017] [Indexed: 11/06/2022] Open
Abstract
Kinesin motors play central roles in establishing and maintaining the mitotic spindle during cell division. Unlike most other kinesins, Cin8, a kinesin-5 motor in Saccharomyces cerevisiae, can move bidirectionally along microtubules, switching directionality according to biochemical conditions, a behavior that remains largely unexplained. To this end, we used biochemical rate and equilibrium constant measurements as well as cryo-electron microscopy methodologies to investigate the microtubule interactions of the Cin8 motor domain. These experiments unexpectedly revealed that, whereas Cin8 ATPase kinetics fell within measured ranges for kinesins (especially kinesin-5 proteins), approximately four motors can bind each αβ-tubulin dimer within the microtubule lattice. This result contrasted with those observations on other known kinesins, which can bind only a single "canonical" site per tubulin dimer. Competition assays with human kinesin-5 (Eg5) only partially abrogated this behavior, indicating that Cin8 binds microtubules not only at the canonical site, but also one or more separate ("noncanonical") sites. Moreover, we found that deleting the large, class-specific insert in the microtubule-binding loop 8 reverts Cin8 to one motor per αβ-tubulin in the microtubule. The novel microtubule-binding mode of Cin8 identified here provides a potential explanation for Cin8 clustering along microtubules and potentially may contribute to the mechanism for direction reversal.
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Affiliation(s)
- Kayla M Bell
- From the Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405
| | - Hyo Keun Cha
- the Department of Cell Biology, Yale School of Medicine, and
| | - Charles V Sindelar
- the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Jared C Cochran
- From the Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405,
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7
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Phillips RK, Peter LG, Gilbert SP, Rayment I. Family-specific Kinesin Structures Reveal Neck-linker Length Based on Initiation of the Coiled-coil. J Biol Chem 2016; 291:20372-86. [PMID: 27462072 DOI: 10.1074/jbc.m116.737577] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Indexed: 12/24/2022] Open
Abstract
Kinesin-1, -2, -5, and -7 generate processive hand-over-hand 8-nm steps to transport intracellular cargoes toward the microtubule plus end. This processive motility requires gating mechanisms to coordinate the mechanochemical cycles of the two motor heads to sustain the processive run. A key structural element believed to regulate the degree of processivity is the neck-linker, a short peptide of 12-18 residues, which connects the motor domain to its coiled-coil stalk. Although a shorter neck-linker has been correlated with longer run lengths, the structural data to support this hypothesis have been lacking. To test this hypothesis, seven kinesin structures were determined by x-ray crystallography. Each included the neck-linker motif, followed by helix α7 that constitutes the start of the coiled-coil stalk. In the majority of the structures, the neck-linker length differed from predictions because helix α7, which initiates the coiled-coil, started earlier in the sequence than predicted. A further examination of structures in the Protein Data Bank reveals that there is a great disparity between the predicted and observed starting residues. This suggests that an accurate prediction of the start of a coiled-coil is currently difficult to achieve. These results are significant because they now exclude simple comparisons between members of the kinesin superfamily and add a further layer of complexity when interpreting the results of mutagenesis or protein fusion. They also re-emphasize the need to consider factors beyond the kinesin neck-linker motif when attempting to understand how inter-head communication is tuned to achieve the degree of processivity required for cellular function.
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Affiliation(s)
- Rebecca K Phillips
- From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706 and
| | - Logan G Peter
- From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706 and
| | - Susan P Gilbert
- the Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Ivan Rayment
- From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706 and
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8
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Cochran JC. Kinesin Motor Enzymology: Chemistry, Structure, and Physics of Nanoscale Molecular Machines. Biophys Rev 2015; 7:269-299. [PMID: 28510227 DOI: 10.1007/s12551-014-0150-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 11/16/2014] [Indexed: 11/25/2022] Open
Abstract
Molecular motors are enzymes that convert chemical potential energy into controlled kinetic energy for mechanical work inside cells. Understanding the biophysics of these motors is essential for appreciating life as well as apprehending diseases that arise from motor malfunction. This review focuses on kinesin motor enzymology with special emphasis on the literature that reports the chemistry, structure and physics of several different kinesin superfamily members.
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Affiliation(s)
- J C Cochran
- Department of Molecular & Cellular Biochemistry, Indiana University, Simon Hall Room 405C, 212 S. Hawthorne Dr., Bloomington, IN, 47405, USA.
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9
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Albracht CD, Rank KC, Obrzut S, Rayment I, Gilbert SP. Kinesin-2 KIF3AB exhibits novel ATPase characteristics. J Biol Chem 2014; 289:27836-48. [PMID: 25122755 DOI: 10.1074/jbc.m114.583914] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
KIF3AB is an N-terminal processive kinesin-2 family member best known for its role in intraflagellar transport. There has been significant interest in KIF3AB in defining the key principles that underlie the processivity of KIF3AB in comparison with homodimeric processive kinesins. To define the ATPase mechanism and coordination of KIF3A and KIF3B stepping, a presteady-state kinetic analysis was pursued. For these studies, a truncated murine KIF3AB was generated. The results presented show that microtubule association was fast at 5.7 μm(-1) s(-1), followed by rate-limiting ADP release at 12.8 s(-1). ATP binding at 7.5 μm(-1) s(-1) was followed by an ATP-promoted isomerization at 84 s(-1) to form the intermediate poised for ATP hydrolysis, which then occurred at 33 s(-1). ATP hydrolysis was required for dissociation of the microtubule·KIF3AB complex, which was observed at 22 s(-1). The dissociation step showed an apparent affinity for ATP that was very weak (K½,ATP at 133 μm). Moreover, the linear fit of the initial ATP concentration dependence of the dissociation kinetics revealed an apparent second-order rate constant at 0.09 μm(-1) s(-1), which is inconsistent with fast ATP binding at 7.5 μm(-1) s(-1) and a Kd ,ATP at 6.1 μm. These results suggest that ATP binding per se cannot account for the apparent weak K½,ATP at 133 μm. The steady-state ATPase Km ,ATP, as well as the dissociation kinetics, reveal an unusual property of KIF3AB that is not yet well understood and also suggests that the mechanochemistry of KIF3AB is tuned somewhat differently from homodimeric processive kinesins.
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Affiliation(s)
- Clayton D Albracht
- From the Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180 and
| | - Katherine C Rank
- the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - Steven Obrzut
- From the Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180 and
| | - Ivan Rayment
- the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - Susan P Gilbert
- From the Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180 and
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10
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Gonzalez MA, Cope J, Rank KC, Chen CJ, Tittmann P, Rayment I, Gilbert SP, Hoenger A. Common mechanistic themes for the powerstroke of kinesin-14 motors. J Struct Biol 2013; 184:335-44. [PMID: 24099757 PMCID: PMC3851574 DOI: 10.1016/j.jsb.2013.09.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 09/19/2013] [Accepted: 09/25/2013] [Indexed: 01/06/2023]
Abstract
Kar3Cik1 is a heterodimeric kinesin-14 from Saccharomyces cerevisiae involved in spindle formation during mitosis and karyogamy in mating cells. Kar3 represents a canonical kinesin motor domain that interacts with microtubules under the control of ATP-hydrolysis. In vivo, the localization and function of Kar3 is differentially regulated by its interacting stoichiometrically with either Cik1 or Vik1, two closely related motor homology domains that lack the nucleotide-binding site. Indeed, Vik1 structurally resembles the core of a kinesin head. Despite being closely related, Kar3Cik1 and Kar3Vik1 are each responsible for a distinct set of functions in vivo and also display different biochemical behavior in vitro. To determine a structural basis for their distinct functional abilities, we used cryo-electron microscopy and helical reconstruction to investigate the 3-D structure of Kar3Cik1 complexed to microtubules in various nucleotide states and compared our 3-D data of Kar3Cik1 with that of Kar3Vik1 and the homodimeric kinesin-14 Ncd from Drosophila melanogaster. Due to the lack of an X-ray crystal structure of the Cik1 motor homology domain, we predicted the structure of this Cik1 domain based on sequence similarity to its relatives Vik1, Kar3 and Ncd. By molecular docking into our 3-D maps, we produced a detailed near-atomic model of Kar3Cik1 complexed to microtubules in two distinct nucleotide states, a nucleotide-free state and an ATP-bound state. Our data show that despite their functional differences, heterodimeric Kar3Cik1 and Kar3Vik1 and homodimeric Ncd, all share striking structural similarities at distinct nucleotide states indicating a common mechanistic theme within the kinesin-14 family.
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Affiliation(s)
- Miguel A. Gonzalez
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347, USA
| | - Julia Cope
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347, USA
| | - Katherine C. Rank
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Chun Ju Chen
- Department of Biology and the Center for Biotechnology & Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Peter Tittmann
- EMEZ, Swiss Federal Institute of Technology, Hoenggerberg, 8093 Zuerich, Switzerland
| | - Ivan Rayment
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Susan P. Gilbert
- Department of Biology and the Center for Biotechnology & Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Andreas Hoenger
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347, USA
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11
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Kinesin-5: cross-bridging mechanism to targeted clinical therapy. Gene 2013; 531:133-49. [PMID: 23954229 DOI: 10.1016/j.gene.2013.08.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 07/29/2013] [Accepted: 08/02/2013] [Indexed: 12/28/2022]
Abstract
Kinesin motor proteins comprise an ATPase superfamily that works hand in hand with microtubules in every eukaryote. The mitotic kinesins, by virtue of their potential therapeutic role in cancerous cells, have been a major focus of research for the past 28 years since the discovery of the canonical Kinesin-1 heavy chain. Perhaps the simplest player in mitotic spindle assembly, Kinesin-5 (also known as Kif11, Eg5, or kinesin spindle protein, KSP) is a plus-end-directed motor localized to interpolar spindle microtubules and to the spindle poles. Comprised of a homotetramer complex, its function primarily is to slide anti-parallel microtubules apart from one another. Based on multi-faceted analyses of this motor from numerous laboratories over the years, we have learned a great deal about the function of this motor at the atomic level for catalysis and as an integrated element of the cytoskeleton. These data have, in turn, informed the function of motile kinesins on the whole, as well as spearheaded integrative models of the mitotic apparatus in particular and regulation of the microtubule cytoskeleton in general. We review what is known about how this nanomotor works, its place inside the cytoskeleton of cells, and its small-molecule inhibitors that provide a toolbox for understanding motor function and for anticancer treatment in the clinic.
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12
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Kaan HYK, Major J, Tkocz K, Kozielski F, Rosenfeld SS. "Snapshots" of ispinesib-induced conformational changes in the mitotic kinesin Eg5. J Biol Chem 2013; 288:18588-98. [PMID: 23658017 DOI: 10.1074/jbc.m113.462648] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Kinesins comprise a superfamily of molecular motors that drive a wide variety of cellular physiologies, from cytoplasmic transport to formation of the bipolar spindle in mitosis. These differing roles are reflected in corresponding polymorphisms in key kinesin structural elements. One of these is a unique loop and stem motif found in all kinesins and referred to as loop 5 (L5). This loop is longest in the mitotic kinesin Eg5 and is the target for a number of small molecule inhibitors, including ispinesib, which is being used in clinical trials in patients with cancer. In this study, we have used x-ray crystallography to identify a new structure of an Eg5-ispinesib complex and have combined this with transient state kinetics to identify a plausible sequence of conformational changes that occur in response to ispinesib binding. Our results demonstrate that ispinesib-induced structural changes in L5 from Eg5 lead to subsequent changes in the conformation of the switch II loop and helix and in the neck linker. We conclude that L5 in Eg5 simultaneously regulates the structure of both the ATP binding site and the motor's mechanical elements that generate force.
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Affiliation(s)
- Hung Yi Kristal Kaan
- Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, Scotland, United Kingdom
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13
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Cope J, Rank KC, Gilbert SP, Rayment I, Hoenger A. Kar3Vik1 uses a minus-end directed powerstroke for movement along microtubules. PLoS One 2013; 8:e53792. [PMID: 23342004 PMCID: PMC3544905 DOI: 10.1371/journal.pone.0053792] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 12/05/2012] [Indexed: 11/19/2022] Open
Abstract
We have used cryo-electron microscopy (cryo-EM) and helical averaging to examine the 3-D structure of the heterodimeric kinesin-14 Kar3Vik1 complexed to microtubules at a resolution of 2.5 nm. 3-D maps were obtained at key points in Kar3Vik1's nucleotide hydrolysis cycle to gain insight into the mechanism that this motor uses for retrograde motility. In all states where Kar3Vik1 maintained a strong interaction with the microtubule, we found, as observed by cryo-EM, that the motor bound with one head domain while the second head extended outwards. 3-D reconstructions of Kar3Vik1-microtubule complexes revealed that in the nucleotide-free state, the motor's coiled-coil stalk points toward the plus-end of the microtubule. In the ATP-state, the outer head is shown to undergo a large rotation that reorients the stalk ∼75° to point toward the microtubule minus-end. To determine which of the two heads binds to tubulin in each nucleotide state, we employed specific Nanogold®-labeling of Vik1. The resulting maps confirmed that in the nucleotide-free, ATP and ADP+Pi states, Kar3 maintains contact with the microtubule surface, while Vik1 extends away from the microtubule and tracks with the coiled-coil as it rotates towards the microtubule minus-end. While many previous investigations have focused on the mechanisms of homodimeric kinesins, this work presents the first comprehensive study of the powerstroke of a heterodimeric kinesin. The stalk rotation shown here for Kar3Vik1 is highly reminiscent of that reported for the homodimeric kinesin-14 Ncd, emphasizing the conservation of a mechanism for minus-end directed motility.
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Affiliation(s)
- Julia Cope
- The Boulder Laboratory for 3-D Microscopy of Cells, Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Katherine C. Rank
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Susan P. Gilbert
- Department of Biology and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, United States of America
| | - Ivan Rayment
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Andreas Hoenger
- The Boulder Laboratory for 3-D Microscopy of Cells, Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
- * E-mail:
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14
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Goulet A, Moores C. New insights into the mechanism of force generation by kinesin-5 molecular motors. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 304:419-66. [PMID: 23809441 DOI: 10.1016/b978-0-12-407696-9.00008-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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.
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Affiliation(s)
- Adeline Goulet
- Institute of Structural and Molecular Biology, Birkbeck College, London, United Kingdom
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15
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Rank KC, Rayment I. Functional asymmetry in kinesin and dynein dimers. Biol Cell 2012; 105:1-13. [PMID: 23066835 DOI: 10.1111/boc.201200044] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 10/08/2012] [Indexed: 11/28/2022]
Abstract
Active transport along the microtubule lattice is a complex process that involves both the Kinesin and Dynein superfamily of motors. Transportation requires sophisticated regulation much of which occurs through the motor's tail domain. However, a significant portion of this regulation also occurs through structural changes that arise in the motor and the microtubule upon binding. The most obvious structural change being the manifestation of asymmetry. To a first approximation in solution, kinesin dimers exhibit twofold symmetry, and microtubules exhibit helical symmetry. The higher symmetries of both the kinesin dimers and microtubule lattice are lost on formation of the kinesin-microtubule complex. Loss of symmetry has functional consequences such as an asymmetric hand-over-hand mechanism in plus-end-directed kinesins, asymmetric microtubule binding in the Kinesin-14 family, spatially biased stepping in dynein and cooperative binding of additional motors to the microtubule. This review focusses on how the consequences of asymmetry affect regulation of motor heads within a dimer, dimers within an ensemble of motors, and suggests how these asymmetries may affect regulation of active transport within the cell.
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Affiliation(s)
- Katherine C Rank
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
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16
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Goulet A, Behnke-Parks WM, Sindelar CV, Major J, Rosenfeld SS, Moores CA. The structural basis of force generation by the mitotic motor kinesin-5. J Biol Chem 2012; 287:44654-66. [PMID: 23135273 DOI: 10.1074/jbc.m112.404228] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
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.
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Affiliation(s)
- Adeline Goulet
- Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, United Kingdom
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17
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Rank KC, Chen CJ, Cope J, Porche K, Hoenger A, Gilbert SP, Rayment I. Kar3Vik1, a member of the kinesin-14 superfamily, shows a novel kinesin microtubule binding pattern. ACTA ACUST UNITED AC 2012; 197:957-70. [PMID: 22734002 PMCID: PMC3384419 DOI: 10.1083/jcb.201201132] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Kinesin-14 motors generate microtubule minus-end-directed force used in mitosis and meiosis. These motors are dimeric and operate with a nonprocessive powerstroke mechanism, but the role of the second head in motility has been unclear. In Saccharomyces cerevisiae, the Kinesin-14 Kar3 forms a heterodimer with either Vik1 or Cik1. Vik1 contains a motor homology domain that retains microtubule binding properties but lacks a nucleotide binding site. In this case, both heads are implicated in motility. Here, we show through structural determination of a C-terminal heterodimeric Kar3Vik1, electron microscopy, equilibrium binding, and motility that at the start of the cycle, Kar3Vik1 binds to or occludes two αβ-tubulin subunits on adjacent protofilaments. The cycle begins as Vik1 collides with the microtubule followed by Kar3 microtubule association and ADP release, thereby destabilizing the Vik1-microtubule interaction and positioning the motor for the start of the powerstroke. The results indicate that head-head communication is mediated through the adjoining coiled coil.
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Affiliation(s)
- Katherine C Rank
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
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18
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Sargent LM, Hubbs AF, Young SH, Kashon ML, Dinu CZ, Salisbury JL, Benkovic SA, Lowry DT, Murray AR, Kisin ER, Siegrist KJ, Battelli L, Mastovich J, Sturgeon JL, Bunker KL, Shvedova AA, Reynolds SH. Single-walled carbon nanotube-induced mitotic disruption. Mutat Res 2012; 745:28-37. [PMID: 22178868 PMCID: PMC4696046 DOI: 10.1016/j.mrgentox.2011.11.017] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 11/29/2011] [Indexed: 04/08/2023]
Abstract
Carbon nanotubes were among the earliest products of nanotechnology and have many potential applications in medicine, electronics, and manufacturing. The low density, small size, and biological persistence of carbon nanotubes create challenges for exposure control and monitoring and make respiratory exposures to workers likely. We have previously shown mitotic spindle aberrations in cultured primary and immortalized human airway epithelial cells exposed to 24, 48 and 96 μg/cm(2) single-walled carbon nanotubes (SWCNT). To investigate mitotic spindle aberrations at concentrations anticipated in exposed workers, primary and immortalized human airway epithelial cells were exposed to SWCNT for 24-72 h at doses equivalent to 20 weeks of exposure at the Permissible Exposure Limit for particulates not otherwise regulated. We have now demonstrated fragmented centrosomes, disrupted mitotic spindles and aneuploid chromosome number at those doses. The data further demonstrated multipolar mitotic spindles comprised 95% of the disrupted mitoses. The increased multipolar mitotic spindles were associated with an increased number of cells in the G2 phase of mitosis, indicating a mitotic checkpoint response. Nanotubes were observed in association with mitotic spindle microtubules, the centrosomes and condensed chromatin in cells exposed to 0.024, 0.24, 2.4 and 24 μg/cm(2) SWCNT. Three-dimensional reconstructions showed carbon nanotubes within the centrosome structure. The lower doses did not cause cytotoxicity or reduction in colony formation after 24h; however, after three days, significant cytotoxicity was observed in the SWCNT-exposed cells. Colony formation assays showed an increased proliferation seven days after exposure. Our results show significant disruption of the mitotic spindle by SWCNT at occupationally relevant doses. The increased proliferation that was observed in carbon nanotube-exposed cells indicates a greater potential to pass the genetic damage to daughter cells. Disruption of the centrosome is common in many solid tumors including lung cancer. The resulting aneuploidy is an early event in the progression of many cancers, suggesting that it may play a role in both tumorigenesis and tumor progression. These results suggest caution should be used in the handling and processing of carbon nanotubes.
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Affiliation(s)
- L M Sargent
- National Institute for Occupational Safety and Health, Morgantown, WV 26505, United States.
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19
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Affiliation(s)
- Alexander Dömling
- Department of Pharmaceutical Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
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20
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Waitzman JS, Larson AG, Cochran JC, Naber N, Cooke R, Jon Kull F, Pate E, Rice SE. The loop 5 element structurally and kinetically coordinates dimers of the human kinesin-5, Eg5. Biophys J 2012; 101:2760-9. [PMID: 22261065 DOI: 10.1016/j.bpj.2011.10.032] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 09/28/2011] [Accepted: 10/13/2011] [Indexed: 10/14/2022] Open
Abstract
Eg5 is a homotetrameric kinesin-5 motor protein that generates outward force on the overlapping, antiparallel microtubules (MTs) of the mitotic spindle. Upon binding an MT, an Eg5 dimer releases one ADP molecule, undergoes a slow (∼0.5 s(-1)) isomerization, and finally releases a second ADP, adopting a tightly MT-bound, nucleotide-free (APO) conformation. This conformation precedes ATP binding and stepping. Here, we use mutagenesis, steady-state and pre-steady-state kinetics, motility assays, and electron paramagnetic resonance spectroscopy to examine Eg5 monomers and dimers as they bind MTs and initiate stepping. We demonstrate that a critical element of Eg5, loop 5 (L5), accelerates ADP release during the initial MT-binding event. Furthermore, our electron paramagnetic resonance data show that L5 mediates the slow isomerization by preventing Eg5 dimer heads from binding the MT until they release ADP. Finally, we find that Eg5 having a seven-residue deletion within L5 can still hydrolyze ATP and move along MTs, suggesting that L5 is not required to accelerate subsequent steps of the motor along the MT. Taken together, these properties of L5 explain the kinetic effects of L5-directed inhibition on Eg5 activity and may direct further interventions targeting Eg5 activity.
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Affiliation(s)
- Joshua S Waitzman
- Department of Cell and Molecular Biology, Northwestern University, Chicago, Illinois, USA
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21
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Bouchet-Marquis C, Pagratis M, Kirmse R, Hoenger A. Metallothionein as a clonable high-density marker for cryo-electron microscopy. J Struct Biol 2012; 177:119-27. [PMID: 22068155 PMCID: PMC3261350 DOI: 10.1016/j.jsb.2011.10.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 10/21/2011] [Accepted: 10/24/2011] [Indexed: 11/24/2022]
Abstract
Cryo-electron microscopy is expanding its scope from macromolecules towards much larger and more complex cellular specimens such as organelles, cells and entire tissues. While isolated macromolecular specimens are typically composed of only very few different components that may be recognized by their shape, size or state of polymerization, cellular specimens combine large numbers of proteinaceous structures as well as nucleic acids and lipid arrays. Consequently, an unambiguous identification of these structures within the context of a whole cell may create a very difficult challenge. On plastic-embedded specimens, or Tokuyasu sections (Tokuyasu, 1980), epitopes that are exposed at the surface can be tagged by antibodies. However, vitrified sections have to be kept at strict cryo-conditions (below -140 °C) and therefore do not allow any post-sectioning treatment of the specimens other than data acquisition in the microscope. Hence, the labels have to be placed into the specimen before freezing. Here we report on the application of a small metal-clustering protein, metallothionein (MTH), as a clonable label capable of clustering metal atoms into a high-density particle with high spatial resolution. We tested MTH as a label for kinesin-decorated microtubules (MTs) as well as the building blocks of desmin intermediate filaments (IFs).
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Affiliation(s)
| | | | | | - Andreas Hoenger
- Dept. of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder CO, 80309-0347, USA
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22
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DREBLOW KERSTIN, KALCHISHKOVA NIKOLINA, BÖHM KONRADJ. KINESIN BYPASSING BLOCKAGES ON MICROTUBULE RAILS. ACTA ACUST UNITED AC 2011. [DOI: 10.1142/s1793048009000958] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Kinesins are motor proteins which convert the chemical energy of ATP into mechanical energy to move along proteinaceous microtubule rails and to transport different cargoes to defined intracellular destinations. It is well documented that following the track of a single protofilament is the thermodynamically most effective mechanism of kinesin movement along microtubules. However, the question arises what happens when a kinesin molecule encounters a hindrance along the protofilament. The present study describes a simple, cell-free approach which enables to study the effects of structural blockages on kinesin-based transport. This experimental approach uses dimeric conventional kinesin moving nanometre-sized gold beads along immobilized microtubules whose surface has been irreversibly decorated by blocking proteins. We demonstrated that the continuous bead transport temporarily stopped at sites of blockages, but usually continued after a certain resting time. Our results suggest that single dimeric kinesin molecules are able to change to another protofilament if the next tubulin dimer where the second head should bind is blocked. A bypassing mechanism is discussed which is considered to be one fundamental prerequisite to realize a kinesin-mediated cargo-transport along microtubules over long distances, required for e.g., the fast axonal transport in motor neurons.
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Affiliation(s)
- KERSTIN DREBLOW
- Leibniz Institute for Age Research – Fritz Lipmann Institute, Beutenbergstraße 11, 07745 Jena, Germany
| | - NIKOLINA KALCHISHKOVA
- Leibniz Institute for Age Research – Fritz Lipmann Institute, Beutenbergstraße 11, 07745 Jena, Germany
| | - KONRAD J. BÖHM
- Leibniz Institute for Age Research – Fritz Lipmann Institute, Beutenbergstraße 11, 07745 Jena, Germany
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23
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Sardar HS, Luczak VG, Lopez MM, Lister BC, Gilbert SP. Mitotic kinesin CENP-E promotes microtubule plus-end elongation. Curr Biol 2011; 20:1648-53. [PMID: 20797864 DOI: 10.1016/j.cub.2010.08.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 07/15/2010] [Accepted: 08/03/2010] [Indexed: 01/26/2023]
Abstract
Centromere protein CENP-E is a dimeric kinesin (Kinesin-7 family) with critical roles in mitosis, including establishment of microtubule (MT)-chromosome linkage and movement of mono-oriented chromosomes on kinetochore microtubules for proper alignment at metaphase [1-9]. We performed studies to test the hypothesis that CENP-E promotes MT elongation at the MT plus ends. A human CENP-E construct was engineered, expressed, and purified, and it yielded the CENP-E-6His dimeric motor protein. The results show that CENP-E promotes MT plus-end-directed MT gliding at 11 nm/s. The results from real-time microscopy assays indicate that 60.3% of polarity-marked MTs exhibited CENP-E-promoted MT plus-end elongation. The MT extension required ATP turnover, and MT plus-end elongation occurred at 1.48 μm/30 min. Immunolocalization studies revealed that 80.8% of plus-end-elongated MTs showed CENP-E at the MT plus end. The time dependence of CENP-E-promoted MT elongation in solution best fit a single exponential function (k(obs) = 5.1 s(-1)), which is indicative of a mechanism in which α,β-tubulin subunit addition is tightly coupled to ATP turnover. Based on these results, we propose that CENP-E, as part of its function in chromosome kinetochore-MT linkage, plays a direct role in MT elongation.
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Affiliation(s)
- Harjinder S Sardar
- Department of Biology, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
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24
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Liu L, Parameswaran S, Liu J, Kim S, Wojcik EJ. Loop 5-directed compounds inhibit chimeric kinesin-5 motors: implications for conserved allosteric mechanisms. J Biol Chem 2010; 286:6201-10. [PMID: 21127071 DOI: 10.1074/jbc.m110.154989] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human Eg5 (HsEg5) protein is unique in its sensitivity to allosteric agents even among phylogenetic kin. For example, S-trityl-l-cysteine (STC) and monastrol are HsEg5 inhibitors that bind to a surface pocket created by the L5 loop, but neither compound inhibits the Drosophila Kinesin-5 homologue (Klp61F). Herein we ask whether or not drug sensitivity can be designed into Klp61F. Two chimeric Klp61F motor domains were engineered, bacterially expressed, and purified to test this idea. We report that effector binding can elicit a robust allosteric response comparable with HsEg5 in both motor domain chimeras. Furthermore, isothermal titration calorimetry confirms that the Klp61F chimeras have de novo binding affinities for both STC and monastrol. These data show that the mechanism of intramolecular communication between the three ligand binding sites is conserved in the Kinesin-5 family, and reconstitution of a drug binding cassette within the L5 pocket is sufficient to restore allosteric inhibition. However, the two compounds were not equivalent in their allosteric inhibition. This surprising disparity in the response between the chimeras to monastrol and STC suggests that there is more than one allosteric communication network for these effectors.
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Affiliation(s)
- Liqiong Liu
- Department of Biochemistry and Molecular Biology, LSU Health Sciences Center, New Orleans, Louisiana 70112, USA
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25
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Larson AG, Naber N, Cooke R, Pate E, Rice SE. The conserved L5 loop establishes the pre-powerstroke conformation of the Kinesin-5 motor, eg5. Biophys J 2010; 98:2619-27. [PMID: 20513406 DOI: 10.1016/j.bpj.2010.03.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Revised: 02/12/2010] [Accepted: 03/09/2010] [Indexed: 11/16/2022] Open
Abstract
Kinesin superfamily motor proteins contain a structurally conserved loop near the ATP binding site, termed L5. The function of L5 is unknown, although several drug inhibitors of the mitotic kinesin Eg5 bind to L5. We used electron paramagnetic resonance spectroscopy (EPR) to investigate the function of L5 in Eg5. We site-specifically attached EPR probes to ADP, L5, and the neck linker element that docks along the enzymatic head to drive forward motility on microtubules (MTs). Nucleotide-dependent spectral mobility shifts occurred in all of these structural elements, suggesting that they undergo coupled conformational changes. These spectral shifts were altered by deletion of L5 or addition of S-trityl-l-cysteine (STLC), an allosteric inhibitor that binds to L5. In particular, EPR probes attached to the neck linker of MT-bound Eg5 shifted to a more immobilized component in the nucleotide-free state relative to the ADP-bound state, consistent with the neck linker docking upon ADP release. In contrast, after L5 deletion or STLC addition, EPR spectra were highly immobilized in all nucleotide states. We conclude that L5 undergoes a conformational change that enables Eg5 to bind to MTs in a pre-powerstroke state. Deletion or inhibition of L5 with the small-molecule inhibitor STLC blocks this pre-powerstroke state, forcing the Eg5 neck linker to dock regardless of the nucleotide state.
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Affiliation(s)
- Adam G Larson
- Department of Cell and Molecular Biology, Northwestern University, Chicago, Illinois, USA
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26
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Learman SS, Kim CD, Stevens NS, Kim S, Wojcik EJ, Walker RA. NSC 622124 inhibits human Eg5 and other kinesins via interaction with the conserved microtubule-binding site. Biochemistry 2010; 48:1754-62. [PMID: 19236100 DOI: 10.1021/bi801291q] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Kinesin-5 proteins are essential for formation of a bipolar mitotic spindle in most and, perhaps all, eukaryotic cells. Several Kinesin-5 proteins, notably the human version, HsEg5, are targets of a constantly expanding group of small-molecule inhibitors, which hold promise both as tools for probing mechanochemical transduction and as anticancer agents. Although most such compounds are selective for HsEg5 and closely related Kinesin-5 proteins, some, such as NSC 622124, exhibit activity against at least one kinesin from outside the Kinesin-5 family. Here we show NSC 622124, despite identification in a screen that yielded inhibitors now known to target the HsEg5 monastrol-binding site, does not compete with [(14)C]monastrol for binding to HsEg5 and is able to inhibit the basal and microtubule-stimulated ATPase activity of the monastrol-insensitive Kinesin-5, KLP61F. NSC 622124 competes with microtubules, but not ATP, for interaction with HsEg5 and disrupts the microtubule binding of HsEg5, KLP61F, and Kinesin-1. Proteolytic degradation of an HsEg5.NSC622124 complex revealed that segments of the alpha3 and alpha5 helices map to the inhibitor-binding site. Overall, our results demonstrate that NSC 622124 targets the conserved microtubule-binding site of kinesin proteins. Further, unlike compounds previously reported to target the kinesin microtubule-binding site, NSC 622124 does not produce any enhancement of basal ATPase activity and thus acts solely as a negative regulator through interaction with a site traditionally viewed as a binding region for positive regulators (i.e., microtubules). Our work emphasizes the concept that microtubule-dependent motor proteins may be controlled at multiple sites by both positive and negative effectors.
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Affiliation(s)
- Sarah S Learman
- Department of Biological Sciences, 2119 Derring Hall, Virginia Tech, Blacksburg, Virginia 24061-0406, USA
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27
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Lakämper S, Thiede C, Düselder A, Reiter S, Korneev MJ, Kapitein LC, Peterman EJG, Schmidt CF. The effect of monastrol on the processive motility of a dimeric kinesin-5 head/kinesin-1 stalk chimera. J Mol Biol 2010; 399:1-8. [PMID: 20227420 DOI: 10.1016/j.jmb.2010.03.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 02/26/2010] [Accepted: 03/03/2010] [Indexed: 12/24/2022]
Abstract
Controlled activity of several kinesin motors is required for the proper assembly of the mitotic spindle. Eg5, a homotetrameric bipolar kinesin-5 from Xenopus laevis, can cross-link and slide anti-parallel microtubules apart by a motility mechanism comprising diffusional and directional modes. How this mechanism is regulated, possibly by the tail domains of the opposing motors, is poorly understood. In order to explore the basic unregulated kinesin-5 motor activity, we generated a stably dimeric kinesin-5 construct, Eg5Kin, consisting of the motor domain and neck linker of Eg5 and the neck coiled coil of Drosophila melanogaster kinesin-1 (DmKHC). In single-molecule motility assays, we found this chimera to be highly processive. In addition, we studied the effect of the kinesin-5-specific inhibitor monastrol using single-molecule fluorescence assays. We found that monastrol reduced the length of processive runs, but strikingly did not affect velocity. Quantitative analysis of monastrol dose dependence suggests that two bound monastrol molecules are required to be bound to an Eg5Kin dimer to terminate a run.
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Affiliation(s)
- Stefan Lakämper
- Drittes Physikalisches Institut, Georg-August-Universität Göttingen, Göttingen, Germany.
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28
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Abstract
Almost 25 years of kinesin research have led to the accumulation of a large body of knowledge about this widespread superfamily of motor and nonmotor proteins present in all eukaryotic cells. This review covers developments in kinesin research with an emphasis on structural aspects obtained by X-ray crystallography and cryoelectron microscopy 3-D analysis on kinesin motor domains complexed to microtubules.
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Affiliation(s)
- Alexander Marx
- Max-Planck-Unit for Structural Molecular Biology, c/o DESY, Hamburg, Germany.
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29
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Ally S, Larson AG, Barlan K, Rice SE, Gelfand VI. Opposite-polarity motors activate one another to trigger cargo transport in live cells. ACTA ACUST UNITED AC 2010; 187:1071-82. [PMID: 20038680 PMCID: PMC2806283 DOI: 10.1083/jcb.200908075] [Citation(s) in RCA: 158] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intracellular transport is typically bidirectional, consisting of a series of back and forth movements. Kinesin-1 and cytoplasmic dynein require each other for bidirectional transport of intracellular cargo along microtubules; i.e., inhibition or depletion of kinesin-1 abolishes dynein-driven cargo transport and vice versa. Using Drosophila melanogaster S2 cells, we demonstrate that replacement of endogenous kinesin-1 or dynein with an unrelated, peroxisome-targeted motor of the same directionality activates peroxisome transport in the opposite direction. However, motility-deficient versions of motors, which retain the ability to bind microtubules and hydrolyze adenosine triphosphate, do not activate peroxisome motility. Thus, any pair of opposite-polarity motors, provided they move along microtubules, can activate one another. These results demonstrate that mechanical interactions between opposite-polarity motors are necessary and sufficient for bidirectional organelle transport in live cells.
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Affiliation(s)
- Shabeen Ally
- Department of Cell and Molecular Biology, Northwestern University, Chicago, IL 60611, USA
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30
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Cope J, Gilbert S, Rayment I, Mastronarde D, Hoenger A. Cryo-electron tomography of microtubule-kinesin motor complexes. J Struct Biol 2009; 170:257-65. [PMID: 20025975 DOI: 10.1016/j.jsb.2009.12.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Accepted: 12/03/2009] [Indexed: 01/14/2023]
Abstract
Microtubules complexed with molecular motors of the kinesin family or non-motor microtubule associated proteins (MAPs) such as tau or EB1 have been the subject of cryo-electron microcopy based 3-D studies for several years. Most of these studies that targeted complexes with intact microtubules have been carried out by helical 3-D reconstruction, while few were analyzed by single particle approaches or from 2-D crystalline arrays. Helical reconstruction of microtubule-MAP or motor complexes has been extremely successful but by definition, all helical 3-D reconstruction attempts require perfectly helical assemblies, which presents a serious limitation and confines the attempts to 15- or 16-protofilament microtubules, microtubule configurations that are very rare in nature. The rise of cryo-electron tomography within the last few years has now opened a new avenue towards solving 3-D structures of microtubule-MAP complexes that do not form helical assemblies, most importantly for the subject here, all microtubules that exhibit a lattice seam. In addition, not all motor domains or MAPs decorate the microtubule surface regularly enough to match the underlying microtubule lattice, or they adopt conformations that deviate from helical symmetry. Here we demonstrate the power and limitation of cryo-electron tomography using two kinesin motor domains, the monomeric Eg5 motor domain, and the heterodimeric Kar3Vik1 motor. We show here that tomography does not exclude the possibility of post-tomographic averaging when identical sub-volumes can be extracted from tomograms and in both cases we were able to reconstruct 3-D maps of conformations that are not possible to obtain using helical or other averaging-based methods.
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Affiliation(s)
- Julia Cope
- The Boulder Laboratory for 3-D Microscopy of Cells, University of Colorado at Boulder, Department of Molecular, Cellular, and Developmental Biology, Boulder, CO 80309-0347, USA
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31
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An allosteric transition trapped in an intermediate state of a new kinesin-inhibitor complex. Biochem J 2009; 425:55-60. [PMID: 19793049 DOI: 10.1042/bj20091207] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Human kinesin Eg5 plays an essential role in mitosis by separating duplicated centrosomes and establishing the bipolar spindle. Eg5 is an interesting drug target for the development of cancer chemotherapy, with seven inhibitors already in clinical trials. In the present paper, we report the crystal structure of the Eg5 motor domain complexed with a potent antimitotic inhibitor STLC (S-trityl-L-cysteine) to 2.0 A (1 A=0.1 nm) resolution. The Eg5-STLC complex crystallizes in space group P3(2) with three molecules per asymmetric unit. Two of the molecules reveal the final inhibitor-bound state of Eg5, whereby loop L5 has swung downwards to close the inhibitor-binding pocket, helix alpha4 has rotated by approx. 15 degrees and the neck-linker has adopted a docked conformation. The third molecule, however, revealed an unprecedented intermediate state, whereby local changes at the inhibitor-binding pocket have not propagated to structural changes at the switch II cluster and neck-linker. This provides structural evidence for the sequence of drug-induced conformational changes.
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32
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Valentine MT, Block SM. Force and premature binding of ADP can regulate the processivity of individual Eg5 dimers. Biophys J 2009; 97:1671-7. [PMID: 19751672 DOI: 10.1016/j.bpj.2009.07.013] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 07/06/2009] [Accepted: 07/15/2009] [Indexed: 11/16/2022] Open
Abstract
Using a high-resolution optical trapping instrument, we directly observed the processive motions of individual Eg5 dimers over a range of external loads and ATP, ADP, and phosphate concentrations. To constrain possible models for dissociation from the microtubule, we measured Eg5 run lengths and also compared the duration of the last step of a processive run to all previous step durations. We found that the application of large longitudinal forces in either hindering or assisting directions could induce Eg5-microtubule dissociation. At a constant moderate force, maintained with a force clamp, the premature binding of ADP strongly promoted microtubule release by Eg5, whereas the addition of ATP or phosphate had little effect on dissociation. These results imply that run length is determined not only by the load, but also by the concentration and type of nucleotides present, and therefore that the biochemical cycles of the two motor domains of the Eg5 dimer are coordinated to promote processive stepping.
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Affiliation(s)
- Megan T Valentine
- Department of Mechanical Engineering, University of California, Santa Barbara, California, USA.
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33
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Tcherniuk S, van Lis R, Kozielski F, Skoufias DA. Mutations in the human kinesin Eg5 that confer resistance to monastrol and S-trityl-L-cysteine in tumor derived cell lines. Biochem Pharmacol 2009; 79:864-72. [PMID: 19896928 DOI: 10.1016/j.bcp.2009.11.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2009] [Revised: 10/30/2009] [Accepted: 11/02/2009] [Indexed: 01/13/2023]
Abstract
The kinesin Eg5 plays an essential role in bipolar spindle formation. A variety of structurally diverse inhibitors of the human kinesin Eg5, including monastrol and STLC, share the same binding pocket on Eg5, composed by helix alpha2/loop L5, and helix alpha3 of the Eg5 motor domain. Previous biochemical analysis in the inhibitor binding pocket of Eg5 identified key residues in the inhibitor binding pocket of Eg5 that in the presence of either monastrol or STLC exhibited ATPase activities similar to the untreated wild type Eg5. Here we evaluated the ability of full-length human Eg5 carrying point mutations in the drug binding pocket to confer resistance in HeLa and U2OS cells to either monastrol or STLC, as measured by the formation of bipolar spindles. Both transfected cells expressing wild type Eg5 and untransfected cells were equally sensitive to both inhibitors. Expression of Eg5 single point mutants R119A, D130A, L132A, I136A, L214A and E215A conferred significant resistance to monastrol. Certain mutations inducing monastrol resistance such as R119A, D130A and L214A also conferred significant resistance to STLC. For the first time at a cellular level, the propensity of selected Eg5 point mutants to confer drug resistance confirms the target specificity of monastrol and STLC for Eg5. These data also suggest a possible mechanism by which drug resistance may occur in tumors treated with agents targeting Eg5.
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Affiliation(s)
- Sergey Tcherniuk
- Institut de Biologie Structurale, (CEA-CNRS-UJF) J.P.Ebel, Laboratoire des Protéines du Cytosquelette 41 rue Jules Horowitz, 38027 Grenoble Cedex 01, France
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34
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Sargent LM, Shvedova AA, Hubbs AF, Salisbury JL, Benkovic SA, Kashon ML, Lowry DT, Murray AR, Kisin ER, Friend S, McKinstry KT, Battelli L, Reynolds SH. Induction of aneuploidy by single-walled carbon nanotubes. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2009; 50:708-17. [PMID: 19774611 DOI: 10.1002/em.20529] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Engineered carbon nanotubes are newly emerging manufactured particles with potential applications in electronics, computers, aerospace, and medicine. The low density and small size of these biologically persistent particles makes respiratory exposures to workers likely during the production or use of commercial products. The narrow diameter and great length of single-walled carbon nanotubes (SWCNT) suggest the potential to interact with critical biological structures. To examine the potential of nanotubes to induce genetic damage in normal lung cells, cultured primary and immortalized human airway epithelial cells were exposed to SWCNT or a positive control, vanadium pentoxide. After 24 hr of exposure to either SWCNT or vanadium pentoxide, fragmented centrosomes, multiple mitotic spindle poles, anaphase bridges, and aneuploid chromosome number were observed. Confocal microscopy demonstrated nanotubes within the nucleus that were in association with cellular and mitotic tubulin as well as the chromatin. Our results are the first to report disruption of the mitotic spindle by SWCNT. The nanotube bundles are similar to the size of microtubules that form the mitotic spindle and may be incorporated into the mitotic spindle apparatus.
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Affiliation(s)
- L M Sargent
- Toxicology and Molecular Biology Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505, USA.
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35
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Xiong Q, Morphew MK, Schwartz CL, Hoenger AH, Mastronarde DN. CTF determination and correction for low dose tomographic tilt series. J Struct Biol 2009; 168:378-87. [PMID: 19732834 DOI: 10.1016/j.jsb.2009.08.016] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Revised: 08/27/2009] [Accepted: 08/29/2009] [Indexed: 11/30/2022]
Abstract
The resolution of cryo-electron tomography can be limited by the first zero of the microscope's contrast transfer function (CTF). To achieve higher resolution, it is critical to determine the CTF and correct its phase inversions. However, the extremely low signal-to-noise ratio (SNR) and the defocus gradient in the projections of tilted specimens make this process challenging. Two programs, CTFPLOTTER and CTFPHASEFLIP, have been developed to address these issues. CTFPLOTTER obtains a 1D power spectrum by periodogram averaging and rotational averaging and it estimates the noise background with a novel approach, which uses images taken with no specimen. The background-subtracted 1D power spectra from image regions at different defocus values are then shifted to align their first zeros and averaged together. This averaging improves the SNR sufficiently that it becomes possible to determine the defocus for subsets of the tilt series rather than just the entire series. CTFPHASEFLIP corrects images line-by-line by inverting phases appropriately in thin strips of the image at nearly constant defocus. CTF correction by these methods is shown to improve the resolution of aligned, averaged particles extracted from tomograms. However, some restoration of Fourier amplitudes at high frequencies is important for seeing the benefits from CTF correction.
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Affiliation(s)
- Quanren Xiong
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
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36
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9-Angström structure of a microtubule-bound mitotic motor. J Mol Biol 2009; 388:218-24. [PMID: 19285086 DOI: 10.1016/j.jmb.2009.03.008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 02/28/2009] [Accepted: 03/04/2009] [Indexed: 12/26/2022]
Abstract
Kinesin-5 (K5) motors are important components of the microtubule (MT)-based cell division machinery and are targets for small-molecule inhibitors currently in cancer clinical trials. However, the nature of the K5-MT interaction and the regulatory mechanisms that control it remain unclear. Using cryo-electron microscopy and image processing, we calculated the structure of a K5 motor bound to MTs at 9 A resolution, providing insight into this important interaction. Our reconstruction reveals the K5 motor domain in an ATP-like conformation in which MT binding induces the conserved nucleotide-sensing switch I and II loops to form a compact subdomain around the bound nucleotide. Our reconstruction also reveals a novel conformation for the K5-specific drug-binding loop 5, suggesting a possible role for it in switching K5s between force generation and diffusional modes of MT binding. Our data thus shed light on regulation of the interaction between spindle components important for chromosome segregation.
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37
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Abstract
Chromosome segregation in eukaryotes requires a large molecular assembly termed the kinetochore to attach chromosomes to spindle microtubules. Recent work has made substantial progress in defining the composition and activities of the kinetochore, but much remains to be learned about its macromolecular structure. This commentary discusses recent insights into structural features of the kinetochore, how these inform our understanding of its biological function, and the key challenges for the future.
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Affiliation(s)
- Julie P I Welburn
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Nine Cambridge Center, Cambridge, MA 02142, USA.
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38
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Cochran JC, Sindelar CV, Mulko NK, Collins KA, Kong SE, Hawley RS, Kull FJ. ATPase cycle of the nonmotile kinesin NOD allows microtubule end tracking and drives chromosome movement. Cell 2009; 136:110-22. [PMID: 19135893 DOI: 10.1016/j.cell.2008.11.048] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 09/23/2008] [Accepted: 11/21/2008] [Indexed: 10/21/2022]
Abstract
Segregation of nonexchange chromosomes during Drosophila melanogaster meiosis requires the proper function of NOD, a nonmotile kinesin-10. We have determined the X-ray crystal structure of the NOD catalytic domain in the ADP- and AMPPNP-bound states. These structures reveal an alternate conformation of the microtubule binding region as well as a nucleotide-sensitive relay of hydrogen bonds at the active site. Additionally, a cryo-electron microscopy reconstruction of the nucleotide-free microtubule-NOD complex shows an atypical binding orientation. Thermodynamic studies show that NOD binds tightly to microtubules in the nucleotide-free state, yet other nucleotide states, including AMPPNP, are weakened. Our pre-steady-state kinetic analysis demonstrates that NOD interaction with microtubules occurs slowly with weak activation of ADP product release. Upon rapid substrate binding, NOD detaches from the microtubule prior to the rate-limiting step of ATP hydrolysis, which is also atypical for a kinesin. We propose a model for NOD's microtubule plus-end tracking that drives chromosome movement.
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Affiliation(s)
- Jared C Cochran
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA
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39
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Marshall CG, Torrent M, Williams O, Hamilton KA, Buser CA. Characterization of inhibitor binding to human kinesin spindle protein by site-directed mutagenesis. Arch Biochem Biophys 2009; 484:1-7. [PMID: 19467625 DOI: 10.1016/j.abb.2009.01.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2008] [Revised: 01/14/2009] [Accepted: 01/15/2009] [Indexed: 11/19/2022]
Abstract
A number of inhibitors of kinesin spindle protein (KSP) have been described, which are known from X-ray crystallography studies to bind to an induced fit pocket defined by the L5 loop. We describe the characterization of eight mutant forms of KSP in which six residues that line this pocket have been altered. Mutants were analyzed by measuring rates of enzyme catalysis, in the presence and absence of six KSP inhibitors of four diverse structural classes and of varied ATP-competition status. Our analysis was in agreement with the model of binding established by the structural studies and suggests that binding energy is well distributed across functional groups in these molecules. The majority of the mutants retained significant enzymatic activity while diminishing inhibitor binding, indicating potential for the development of drug resistance. These data provide detailed information on interactions between inhibitor and binding pocket at the functional group level and enable the development of novel KSP inhibitors.
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Affiliation(s)
- C Gary Marshall
- Dept. of Cancer Biology and Therapeutics, Merck Research Laboratories, 33 Avenue Louis Pasteur, Boston, MA 02115, USA.
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40
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Müller SA, Aebi U, Engel A. What transmission electron microscopes can visualize now and in the future. J Struct Biol 2008; 163:235-45. [PMID: 18614377 DOI: 10.1016/j.jsb.2008.05.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Accepted: 05/21/2008] [Indexed: 11/18/2022]
Abstract
Our review concentrates on the progress made in high-resolution transmission electron microscopy (TEM) in the past decade. This includes significant improvements in sample preparation by quick-freezing aimed at preserving the specimen in a close-to-native state in the high vacuum of the microscope. Following advances in cold stage and TEM vacuum technology systems, the observation of native, frozen hydrated specimens has become a widely used approach. It fostered the development of computer guided, fully automated low-dose data acquisition systems allowing matched pairs of images and diffraction patterns to be recorded for electron crystallography, and the collection of entire tilt-series for electron tomography. To achieve optimal information transfer to atomic resolution, field emission electron guns combined with acceleration voltages of 200-300 kV are now routinely used. The outcome of these advances is illustrated by the atomic structure of mammalian aquaporin-O and by the pore-forming bacterial cytotoxin ClyA resolved to 12 A. Further, the Yersinia injectisome needle, a bacterial pseudopilus and the binding of phalloidin to muscle actin filaments were chosen to document the advantage of the high contrast offered by dedicated scanning transmission electron microscopy (STEM) and/or the STEM's ability to measure the mass of protein complexes and directly link this to their shape. Continued progress emerging from leading research laboratories and microscope manufacturers will eventually enable us to determine the proteome of a single cell by electron tomography, and to more routinely solve the atomic structure of membrane proteins by electron crystallography.
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Affiliation(s)
- Shirley A Müller
- Maurice E. Müller Institute for Structural Biology, Biozentrum, University of Basel, Klingelbergstr. 70, CH-4056 Basel, Switzerland.
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41
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42
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Krzysiak TC, Grabe M, Gilbert SP. Getting in sync with dimeric Eg5. Initiation and regulation of the processive run. J Biol Chem 2007; 283:2078-87. [PMID: 18037705 DOI: 10.1074/jbc.m708354200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
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.
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Affiliation(s)
- Troy C Krzysiak
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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43
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Rickert KW, Schaber M, Torrent M, Neilson LA, Tasber ES, Garbaccio R, Coleman PJ, Harvey D, Zhang Y, Yang Y, Marshall G, Lee L, Walsh ES, Hamilton K, Buser CA. Discovery and biochemical characterization of selective ATP competitive inhibitors of the human mitotic kinesin KSP. Arch Biochem Biophys 2007; 469:220-31. [PMID: 17999913 DOI: 10.1016/j.abb.2007.10.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Revised: 10/12/2007] [Accepted: 10/13/2007] [Indexed: 10/22/2022]
Abstract
The kinesin spindle protein (KSP, also known as Eg5) is essential for the proper separation of spindle poles during mitosis, and inhibition results in mitotic arrest and the formation of characteristic monoaster spindles. Several distinct classes of KSP inhibitors have been described previously in the public and patent literature. However, most appear to share a common induced-fit allosteric binding site, suggesting a common mechanism of inhibition. In a high-throughput screen for inhibitors of KSP, a novel class of thiazole-containing inhibitors was identified. Unlike the previously described allosteric KSP inhibitors, the thiazoles described here show ATP competitive kinetic behavior, consistent with binding within the nucleotide binding pocket. Although they bind to a pocket that is highly conserved across kinesins, these molecules exhibit significant selectivity for KSP over other kinesins and other ATP-utilizing enzymes. Several of these compounds are active in cells and produce a phenotype similar to that observed with previously published allosteric inhibitors of KSP.
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Affiliation(s)
- Keith W Rickert
- Department of Cancer Research, Merck Research Laboratories, P.O. Box 4, West Point, PA 19486, USA.
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44
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Valentine MT, Gilbert SP. To step or not to step? How biochemistry and mechanics influence processivity in Kinesin and Eg5. Curr Opin Cell Biol 2007; 19:75-81. [PMID: 17188855 PMCID: PMC2270473 DOI: 10.1016/j.ceb.2006.12.011] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2006] [Accepted: 12/08/2006] [Indexed: 11/29/2022]
Abstract
Conventional kinesin and Eg5 are essential nanoscale motor proteins. Single-molecule and presteady-state kinetic experiments indicate that both motors use similar strategies to generate movement along microtubules, despite having distinctly different in vivo functions. Single molecules of kinesin, a long-distance cargo transporter, are highly processive, binding the microtubule and taking 100 or more sequential steps at velocities of up to 700 nm/s before dissociating, whereas Eg5, a motor active in mitotic spindle assembly, is also processive, but takes fewer steps at a slower rate. By dissecting the structural, biochemical and mechanical features of these proteins, we hope to learn how kinesin and Eg5 are optimized for their specific biological tasks, while gaining insight into how biochemical energy is converted into mechanical work.
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Affiliation(s)
- Megan T Valentine
- Department of Biological Sciences Stanford University 030 Herrin Labs Stanford, CA 94305 650-724-5536 USA
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45
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Affiliation(s)
- Andreas Hoenger
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA
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46
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Abstract
Understanding how molecular motors generate force and move microtubules in mitosis is essential to understanding the physical mechanism of cell division. Recent measurements have shown that one mitotic kinesin superfamily member, Eg5, is mechanically processive and capable of crosslinking and sliding microtubules in vitro. In this review, we highlight recent work that explores how Eg5 functions under load, with an emphasis on the nanomechanical properties of single enzymes.
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Affiliation(s)
- Megan T Valentine
- Department of Biological Sciences, Stanford University, Stanford CA 94305, USA
| | - Polly M Fordyce
- Department of Physics, Stanford University, Stanford CA 94305, USA
| | - Steven M Block
- Department of Biological Sciences, Stanford University, Stanford CA 94305, USA
- Department of Applied Physics, Stanford University, Stanford CA 94305, USA
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47
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Abstract
Kinesin-5 family members including human Eg5/KSP contribute to the plus-end-directed force necessary for the assembly and maintenance of the bipolar mitotic spindle. We have used monomeric Eg5-367 in the nucleotide-free state to evaluate the role of microtubules at each step in the ATPase cycle. The pre-steady-state kinetic results show that the microtubule-Eg5 complex binds MgATP tightly, followed by rapid ATP hydrolysis with a subsequent slow step that limits steady-state turnover. We show that microtubules accelerate the kinetics of each step in the ATPase pathway, suggesting that microtubules amplify the nucleotide-dependent structural transitions required for force generation. The experimentally determined rate constants for phosphate product release and Eg5 detachment from the microtubule were similar, suggesting that these two steps are coupled with one occurring at the slow rate after ATP hydrolysis followed by the second step occurring more rapidly. The rate of this slow step correlates well with the steady-state k(cat), indicative that it is the rate-limiting step of the mechanism.
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Affiliation(s)
| | | | - Susan P. Gilbert
- * Corresponding author. Tel: 412-624-5842. Fax: 412-624-4759. E-mail:
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48
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Krzysiak TC, Gilbert SP. Dimeric Eg5 maintains processivity through alternating-site catalysis with rate-limiting ATP hydrolysis. J Biol Chem 2006; 281:39444-54. [PMID: 17062577 PMCID: PMC1866285 DOI: 10.1074/jbc.m608056200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Eg5/KSP is a homotetrameric, Kinesin-5 family member whose ability to cross-link microtubules has associated it with mitotic spindle assembly and dynamics for chromosome segregation. Transient-state kinetic methodologies have been used to dissect the mechanochemical cycle of a dimeric motor, Eg5-513, to better understand the cooperative interactions that modulate processive stepping. Microtubule association, ADP release, and ATP binding are all fast steps in the pathway. However, the acid-quench analysis of the kinetics of ATP hydrolysis with substrate in excess of motor was unable to resolve a burst of product formation during the first turnover event. In addition, the kinetics of P(i) release and ATP-promoted microtubule-Eg5 dissociation were observed to be no faster than the rate of ATP hydrolysis. In combination the data suggest that dimeric Eg5 is the first kinesin motor identified to have a rate-limiting ATP hydrolysis step. Furthermore, several lines of evidence implicate alternating-site catalysis as the molecular mechanism underlying dimeric Eg5 processivity. Both mantATP binding and mantADP release transients are biphasic. Analysis of ATP hydrolysis through single turnover assays indicates a surprising substrate concentration dependence, where the observed rate is reduced by half when substrate concentration is sufficiently high to require both motor domains of the dimer to participate in the reaction.
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Affiliation(s)
- Troy C Krzysiak
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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49
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Neumann E, Garcia-Saez I, DeBonis S, Wade RH, Kozielski F, Conway JF. Human Kinetochore-associated Kinesin CENP-E Visualized at 17 Å Resolution Bound to Microtubules. J Mol Biol 2006; 362:203-11. [PMID: 16926026 DOI: 10.1016/j.jmb.2006.07.042] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Revised: 07/07/2006] [Accepted: 07/20/2006] [Indexed: 11/23/2022]
Abstract
The highly dynamic process of cell division is effected, in part, by molecular motors that generate the forces necessary for its enactment. Several members of the kinesin superfamily of motor proteins are implicated in mitosis, such as CENP-E, which plays essential roles in cell division, including association with the kinetochore to stabilize attachment of chromosomes to microtubules prior to and during their separation. Neither the functional assembly state of CENP-E nor its direction of motion along the polar microtubule are certain. To determine the mode of interaction between CENP-E and microtubules, we have used cryo-electron microscopy to visualize CENP-E motor domains complexed with microtubules and calculated a density map of the complex to 17 A resolution by combining helical and single-particle reconstruction methods. The interface between the motor domain and microtubules was modeled by docking atomic-resolution models of the subunits into the cryoEM density map. Our results support a plus end motion for CENP-E, consistent with features of the crystallographic structure. Despite considerable functional differences from the monomeric transporter kinesin KIF1A and the oppositely directed ncd kinesin, CENP-E appears to share many features of the intermolecular interactions, suggesting that differences in motor function are governed by small variations in the loops at the microtubule interface.
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Affiliation(s)
- E Neumann
- Laboratoire de Microscopie Electronique Structurale, Institut de Biologie Structurale J.-P. Ebel, UMR 5075 CNRS-CEA-UJF, 38027 Grenoble, France
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Kwok BH, Kapitein LC, Kim JH, Peterman EJG, Schmidt CF, Kapoor TM. Allosteric inhibition of kinesin-5 modulates its processive directional motility. Nat Chem Biol 2006; 2:480-5. [PMID: 16892050 DOI: 10.1038/nchembio812] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Accepted: 07/13/2006] [Indexed: 11/08/2022]
Abstract
Small-molecule inhibitors of kinesin-5 (refs. 1-3), a protein essential for eukaryotic cell division, represent alternatives to antimitotic agents that target tubulin. While tubulin is needed for multiple intracellular processes, the known functions of kinesin-5 are limited to dividing cells, making it likely that kinesin-5 inhibitors would have fewer side effects than do tubulin-targeting drugs. Kinesin-5 inhibitors, such as monastrol, act through poorly understood allosteric mechanisms, not competing with ATP binding. Moreover, the microscopic mechanism of full-length kinesin-5 motility is not known. Here we characterize the motile properties and allosteric inhibition of Eg5, a vertebrate kinesin-5, using a GFP fusion protein in single-molecule fluorescence assays. We find that Eg5 is a processive kinesin whose motility includes, in addition to ATP-dependent directional motion, a diffusive component not requiring ATP hydrolysis. Monastrol suppresses the directional processive motility of microtubule-bound Eg5. These data on Eg5's allosteric inhibition will impact these inhibitors' use as probes and development as chemotherapeutic agents.
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Affiliation(s)
- Benjamin H Kwok
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
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