Minus end-directed motor protein that transports actin filaments along microtubules. Plays a central role in the polar orientation of actin filaments along microtubules, and thus a contribution to the organization of the cytoskeletal architecture (PubMed:27250543). Links the actin microfilaments with the cortical microtubules in both cycling and non-cycling cells (PubMed:19561334). Required for efficient cell elongation by its participation in the premitotic nuclear positioning (PubMed:20566563). The microtubule-dependent ATPase activity is regulated by actin binding. Optimum pH is 6.5 for ATPase activity (in presence of microtubules). Forms oligomers in vitro. Interacts with actin microfilaments (PubMed:19561334, PubMed:27250543). Binds to actin in vitro through its calponin-homology (CH) domain (PubMed:21047815). Colocalizes with cortical microtubules and longitudinally oriented actin microfilaments. Expressed in primary leaf, primary root, developing flower and coleoptile. Shorter coleoptiles due to impaired cell expansion and increased division. Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Kinesin family. KIN-14 subfamily.