A small peptide sequence is sufficient for initiating kinesin-1 activation through part of TPR region of KLC1.

Kinesin-1 anterogradely transports vesicles containing cargo proteins when a protein-protein interaction activates it from an inhibited state. The C-terminal cytoplasmic region of kinesin-1 cargo protein Alcadeinα (Alcα) interacts with the KLC1 subunit's tetratricopeptide repeat (TPR) region, activating kinesin-1's association with vesicles and anterograde transport. We found that either of two 10-amino-acid WD motifs in Alcα cytoplasmic region was necessary and sufficient to initiate this activation. An artificial transmembrane protein containing either WD motif induced kinesin-1's vesicular association and anterograde transport in a KLC-dependent manner, even in the normally inhibiting presence of excess KLC1, thus allowing us to analyze the KLC1 TPR-WD functional interaction in detail in vivo. A part of TPR region was dispensable for the WD motifs' activation of kinesin-1 and transport, indicating that only part of the TPR structure is required for this function in vivo. For a different kinesin-1 cargo protein, JIP1, an 11-amino-acid C-terminal region was sufficient to recruit KLC1 to vesicles, but did not activate transport. These observations suggest that structurally different TPR-interacting peptides may have different effects on kinesin-1. This mechanism may partly explain how kinesin-1 can organize the transport of a wide variety of cargo molecules.