ONE OF KINESIN LIGHT-CHAINS SELECTIVELY ASSOCIATES WITH MITOCHONDRIA

The molecule of kinesin, a motor protein responsible for intracellular transport along microtubules, is composed of two heavy and two light chains. Since the light chains are localized on the end of the molecul e opposite to the motor domain, they are usually considered to be invo lved in binding the cargo transported by kinesin. The several isoforms of kinesin light chains are probably responsible for transporting dif ferent organelles. Here we studied the role of the light chains in kin esin binding with the transported cargo. We have isolated five clones coding for different isoforms from the cDNA library of cultured CHO-K1 cells using antibodies specific to all kinesin light chain isoforms. The C-terminal fragment of one of the isoforms was synthesized in bact eria and used as an antigen for isoform-specific antibody production, The obtained antibodies (called anti-B) recognized only one polypeptid e in homogenates of human skin or rat liver fibroblasts. Immunofluores cent experiments demonstrate staining of mitochondria in cultured fibr oblasts by these antibodies. During isolation of mitochondria from rat liver, only one kinesin light chain recognized by anti-B antibodies i s copurified with the mitochondria. Hence, one of light kinesin chains is selectively associated with mitochondria.