The Drosophila kinesin light chain. Primary structure and interaction with kinesin heavy chain.

Kinesin light chain (KLC) complexes with the kinesin heavy chain (KHC) to form native kinesin. Proposed functions of KLC include coupling of cargo to KHC or modulation of KHC ATPase activity. In this paper we use the KHC tail, which binds specifically to KLC in blot overlays, as a probe to clone a cDNA encoding KLC from a Drosophila expression library. The identified clone encodes a protein with 70% amino acid identity to rat KLC. Drosophila KLC is predicted to form an alpha-helical coiled-coil between residues 34 and 129, followed by five imperfect tandem repeats of unknown function and a sixth shorter motif. These repeats are highly conserved across species. The Drosophila KLC gene is located at 69D on the third chromosome and is widely expressed, with 1.8-kb transcripts in most tissues, and slightly smaller transcripts in gonads. Finally, we present evidence that the heptad repeats of KLC are required for interaction with the KHC tail. Since the KHC tail used in our assay includes about 20 heptad repeats, this result suggests that KHC and KLC interact via coiled-coils. Such an interaction could provide stability to the KHC-KLC complex in vivo.