title: Biochemical and molecular dynamic simulation analysis of a weak coiled coil association between kinesin-II stalks.
abstract: BACKGROUND
  Kinesin-2 refers to the family of motor proteins represented by conserved, heterotrimeric kinesin-II and homodimeric Osm3/Kif17 class of motors.
  
  
  BACKGROUND
  Kinesin-II, a microtubule-based anterograde motor, is composed of three different conserved subunits, named KLP64D, KLP68D and DmKAP in Drosophila. Although previous reports indicated that coiled coil interaction between the middle segments of two dissimilar motor subunits established the heterodimer, the molecular basis of the association is still unknown.
  
  
  RESULTS
  Here, we present a detailed heterodimeric association model of the KLP64D/68D stalk supported by extensive experimental analysis and molecular dynamic simulations. We find that KLP64D stalk is unstable, but forms a weak coiled coil heteroduplex with the KLP68D stalk when coexpressed in bacteria. Local instabilities, relative affinities between the C-terminal stalk segments, and dynamic long-range interactions along the stalks specify the heterodimerization. Thermal unfolding studies and independent simulations further suggest that interactions between the C-terminal stalk fragments are comparatively stable, whereas the N-terminal stalk reversibly unfolds at ambient temperature.
  
  
  CONCLUSIONS
  Results obtained in this study suggest that coiled coil interaction between the C-terminal stalks of kinesin-II motor subunits is held together through a few hydrophobic and charged interactions. The N-terminal stalk segments are flexible and could uncoil reversibly during a motor walk. This supports the requirement for a flexible coiled coil association between the motor subunits, and its role in motor function needs to be elucidated.
authors.affiliation: Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India.
authors.forename: Harinath
authors.initials: H
authors.lastname: Doodhi
authors.forename: Swadhin C
authors.initials: SC
authors.lastname: Jana
authors.forename: Pavithra
authors.initials: P
authors.lastname: Devan
authors.forename: Shyamalava
authors.initials: S
authors.lastname: Mazumdar
authors.forename: Krishanu
authors.initials: K
authors.lastname: Ray
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D004330:Drosophila / Q000737:chemistry*; D029721:Drosophila Proteins / Q000737:chemistry* / Q000648:ultrastructure; D016547:Kinesins / Q000737:chemistry* / Q000648:ultrastructure; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D017510:Protein Folding; D055503:Protein Multimerization; D055550:Protein Stability; D017433:Protein Structure, Secondary
chemical_list: D029721:Drosophila Proteins; C090556:KLP68D protein, Drosophila; C486143:KLP64D protein, Drosophila; D016547:Kinesins