The kinesin-immunoreactive homologue from Nicotiana tabacum pollen tubes: Biochemical properties and subcellular localization

In plant cells, microtubule-based motor proteins have not been characterized to the same degree as in animal cells; therefore, it is not yet clear whether the movement of organelles and vesicles is also dependent on the microtubular cytoskeleton. In this work the kinesinimmunoreactive homologue from pollen tubes of Nicotiana tabacum L. has been purified and biochemically characterized. The protein preparation mainly contained a polypeptide with a relative molecular weight of approx. 100 kDa. This polypeptide bound to animal microtubules in an ATP-dependent manner and it further copurified with an ATPase activity fourfold-stimulated by the presence of microtubules. In addition, the sedimentation coefficient (approx. 9S) was similar to those previously shown for other kinesins. Immunofluorescence analyses revealed a partial co-distribution of the protein with microtubules in the pollen tube. These data clearly indicate that several properties of the kinesin-immunoreactive homologue are similar to those of kinesin proteins, and suggest that molecular mechanisms analogous to those of animal cells may drive the microtubule-based motility of organelles and vesicles in plants.Abbreviations AE-LPLC anion-exchange low-pressure liquid chromatography - AMPPNP 5-adenylylimidodiphosphate - PKH pollen kinesin homologue - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis