title: Long tethers provide high-force coupling of the Dam1 ring to shortening microtubules.
abstract: Microtubule kinetochore attachments are essential for accurate mitosis, but how these force-generating connections move chromosomes remains poorly understood. Processive motion at shortening microtubule ends can be reconstituted in vitro using microbeads conjugated to the budding yeast kinetochore protein Dam1, which forms microtubule-encircling rings. Here, we report that, when Dam1 is linked to a bead cargo by elongated protein tethers, the maximum force transmitted from a disassembling microtubule increases sixfold compared with a short tether. We interpret this significant improvement with a theory that considers the geometry and mechanics of the microtubule-ring-bead system. Our results show the importance of fibrillar links in tethering microtubule ends to cargo: fibrils enable the cargo to align coaxially with the microtubule, thereby increasing the stability of attachment and the mechanical work that it can do. The force-transducing characteristics of fibril-tethered Dam1 are similar to the analogous properties of purified yeast kinetochores, suggesting that a tethered Dam1 ring comprises the main force-bearing unit of the native attachment.
authors.affiliation: Laboratory of Biophysics, Federal Research Center of Pediatric Hematology, Oncology and Immunology, Moscow 117198, Russia. vavolkov@gmail.com
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Volkov
authors.forename: Anatoly V
authors.initials: AV
authors.lastname: Zaytsev
authors.forename: Nikita
authors.initials: N
authors.lastname: Gudimchuk
authors.forename: Paula M
authors.initials: PM
authors.lastname: Grissom
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Gintsburg
authors.forename: Fazly I
authors.initials: FI
authors.lastname: Ataullakhanov
authors.forename: J Richard
authors.initials: JR
authors.lastname: McIntosh
authors.forename: Ekaterina L
authors.initials: EL
authors.lastname: Grishchuk
mesh_terms: D000705:Anaphase; D000818:Animals; D001696:Biomechanical Phenomena; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000502:physiology; D004058:Diffusion; D018386:Kinetochores / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000737:chemistry* / Q000502:physiology; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008962:Models, Theoretical; D009218:Myosins / Q000737:chemistry; D052898:Optical Tweezers; D051381:Rats; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000502:physiology; D013314:Stress, Mechanical; D024723:Ventricular Myosins / Q000737:chemistry
chemical_list: D018797:Cell Cycle Proteins; C116003:DAM1 protein, S cerevisiae; D008869:Microtubule-Associated Proteins; D029701:Saccharomyces cerevisiae Proteins; D024723:Ventricular Myosins; D009218:Myosins
keywords: anaphase; forced walk; laser tweezers; mathematical modeling; microtubule depolymerization