KAR3, a kinesin-related gene required for yeast nuclear fusion

Cell. 1990 Mar 23;60(6):1029-41. doi: 10.1016/0092-8674(90)90351-e.


The KAR3 gene is essential for yeast nuclear fusion during mating, and its expression is strongly induced by alpha factor. The predicted KAR3 protein sequence contains two globular domains separated by an alpha-helical coiled coil. The carboxy-terminal domain is homologous to the amino-terminal mechanochemical domain of Drosophila kinesin heavy chain. Mutation of the putative ATP binding site produces a dominant "poison" of nuclear fusion. The mutant protein shows enhanced microtubule association in vivo, as predicted for a kinesin-like protein in a state of rigor binding. Localization of hybrid proteins to cytoplasmic microtubules in shmoos indicates that the amino-terminal domain also contains determinants for microtubule association. Thus, KAR3 is a member of a larger family of kinesin-like proteins characterized by the presence of the mechanochemical domain tethered to different protein binding domains. The phenotypes of kar3 mutants suggest that the protein mediates microtubule sliding during nuclear fusion and possibly mitosis.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphatases / genetics*
  • Adenosine Triphosphate / metabolism
  • Amino Acid Sequence
  • Base Sequence
  • Binding Sites
  • Cell Nucleus / ultrastructure*
  • Fungal Proteins / genetics*
  • Fungal Proteins / metabolism
  • Genes, Fungal*
  • Genetic Complementation Test
  • Genotype
  • Kinesin
  • Microtubule-Associated Proteins*
  • Molecular Sequence Data
  • Mutation
  • Phenotype
  • Plasmids
  • Protein Conformation
  • RNA, Messenger / genetics
  • Restriction Mapping
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins*
  • Sequence Homology, Nucleic Acid


  • Fungal Proteins
  • KAR3 protein, S cerevisiae
  • Microtubule-Associated Proteins
  • RNA, Messenger
  • Saccharomyces cerevisiae Proteins
  • Adenosine Triphosphate
  • Adenosine Triphosphatases
  • Kinesin

Associated data

  • GENBANK/M31719