title: The Dam1 ring binds microtubules strongly enough to be a processive as well as energy-efficient coupler for chromosome motion.
abstract: Accurate chromosome segregation during mitotic division of budding yeast depends on the multiprotein kinetochore complex, Dam1 (also known as DASH). Purified Dam1 heterodecamers encircle microtubules (MTs) to form rings that can function as "couplers," molecular devices that transduce energy from MT disassembly into the motion of a cargo. Here we show that MT depolymerization develops a force against a Dam1 ring that is sixfold larger than the force exerted on a coupler that binds only one side of an MT. Wild-type rings slow depolymerization fourfold, but rings that include a mutant Dam1p with truncated C terminus slow depolymerization less, consistent with the idea that this tail is part of a strong bond between rings and MTs. A molecular-mechanical model for Dam1-MT interaction predicts that binding between this flexible tail and the MT wall should cause a Dam1 ring to wobble, and Fourier analysis of moving, ring-attached beads corroborates this prediction. Comparison of the forces generated against wild-type and mutant complexes confirms the importance of tight Dam1-MT association for processive cargo movement under load.
authors.affiliation: Molecular, Cellular, and Developmental Biology Department, University of Colorado, Boulder, CO 80309, USA. katya@colorado.edu
authors.forename: Ekaterina L
authors.initials: EL
authors.lastname: Grishchuk
authors.forename: Artem K
authors.initials: AK
authors.lastname: Efremov
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Volkov
authors.forename: Ilia S
authors.initials: IS
authors.lastname: Spiridonov
authors.forename: Nikita
authors.initials: N
authors.lastname: Gudimchuk
authors.forename: Stefan
authors.initials: S
authors.lastname: Westermann
authors.forename: David
authors.initials: D
authors.lastname: Drubin
authors.forename: Georjana
authors.initials: G
authors.lastname: Barnes
authors.forename: J Richard
authors.initials: JR
authors.lastname: McIntosh
authors.forename: Fazly I
authors.initials: FI
authors.lastname: Ataullakhanov
mesh_terms: D001696:Biomechanical Phenomena; D020090:Chromosome Segregation; D015825:Chromosomes, Fungal / Q000502:physiology*; D018386:Kinetochores / Q000502:physiology / Q000648:ultrastructure; D008869:Microtubule-Associated Proteins / Q000502:physiology*; D008870:Microtubules / Q000502:physiology*; D008954:Models, Biological; D004718:Saccharomycetales / Q000378:metabolism
chemical_list: D008869:Microtubule-Associated Proteins