An isoform of kinesin light chain specific for the Golgi complex

Conventional kinesin is a motor protein implicated in the transport of a va riety of cytoplasmic organelles along microtubules, The kinesin molecule co nsists of two heavy chains with motor domains at their amino termini and tw o light chains, which, together with the carboxyl termini of the heavy chai ns, are proposed to mediate binding to cargoes. Since the light chains are represented by multiple isoforms diverging at their carboxyl termini they a re presumed to specify kinesin targeting to organelles. Previously, we isol ated five cDNAs, encoding hamster kinesin light chain isoforms, and found t hat one of them (B or C) preferentially associated with mitochondria. To ob tain additional evidence proving the specific location of various kinesin l ight chain isoforms on organelles, we made an antibody against a 56 amino-a cid sequence found at the carboxyl-terminal regions of the hamster D and E isoforms, By indirect immunofluorescence, this antibody specifically labele d the Golgi complex in cultured cells. In western blots of total cell homog enates, it recognized two close polypeptides, one of which co-purified with the Golgi membranes. Thus, the results of this and previous studies demons trate that different kinesin light chains are associated with different org anelles in cells.