THE DROSOPHILA-CLARET SEGREGATION PROTEIN IS A MINUS-END DIRECTED MOTOR MOLECULE

A PRODUCT encoded at the claret locus in Drosophila is needed for normal chromosome segregation in meiosis in females and in early mitotic divisions of the embryo1,2. The predicted amino-acid sequence of the segregation protein was shown recently to be strikingly similar to Drosophila kinesin heavy chain3. We have expressed the claret segregation protein in bacteria and have found that the bacterially expressed protein has motor activity in vitro with several novel features. The claret motor is slow (4 μm min-1), unlike either kinesin or dyneins. It has the directionality, the ability to generate torque and the sensitivity to inhibitors reported previously for dyneins. The finding of minus-end directed motor activity for a protein with sequence similarity to kinesin suggests that the dynein and kinesin motor domains are ancestrally related. The minus-end directed motor activity of the claret motor is consistent with a role for this protein in producing chromosome movement along spindle microtubules during prometaphase and/or anaphase. © 1990 Nature Publishing Group.