title: K-loop insertion restores microtubule depolymerizing activity of a "neckless" MCAK mutant.
abstract: Unlike most kinesins, mitotic centromere-associated kinesin (MCAK) does not translocate along the surface of microtubules (MTs), but instead depolymerizes them. Among the motile kinesins, refinements that are unique for specific cellular functions, such as directionality and processivity, are under the control of a "neck" domain adjacent to the ATP-hydrolyzing motor domain. Despite its apparent lack of motility, MCAK also contains a neck domain. We found that deletions and alanine substitutions of highly conserved positively charged residues in the MCAK neck domain significantly reduced MT depolymerization activity. Furthermore, substitution of MCAK's neck domain with either the positively charged KIF1A K-loop or poly-lysine rescues the loss of MT-depolymerizing activity observed in the neckless MCAK mutant. We propose that the neck, analogously to the K-loop, interacts electrostatically with the tubulin COOH terminus to permit diffusional translocation of MCAK along the surface of MTs. This weak-binding interaction may also play an important role in processivity of MCAK-induced MT depolymerization.
authors.affiliation: Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA.
authors.forename: Yulia
authors.initials: Y
authors.lastname: Ovechkina
authors.forename: Michael
authors.initials: M
authors.lastname: Wagenbach
authors.forename: Linda
authors.initials: L
authors.lastname: Wordeman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D006801:Humans; D016547:Kinesins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D020409:Molecular Motor Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011108:Polymers / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: C091489:KIF2C protein, human; D020409:Molecular Motor Proteins; D011108:Polymers; D011993:Recombinant Fusion Proteins; C490417:mitotic centromere-associated kinesin, hamster; D016547:Kinesins