38 Microtubules in vesicular and organelle transport
Transport of organelles and membrane-bound vesicles in eukaryotic cells is directed along ‘tracks’ of single microtubules by a ‘walking’ mechanism (Fig. 3.38.1). The molecular motors for this movement are myosin-like ATPases, kinesin and dynein. Kinesin drives movement from the (−)-end (centrosome) of the microtubule to the (+)-end while cytoplasmic dynein drives movement in the opposite direction. Since microtubules are usually arranged with their centromeres near the centre of the cell, kinesin drives anterograde movement from the centre to the periphery, while dynein drives retrograde movement towards the centre. The ATP-dependent attachment of kinesin or dynein head groups to the microtubule drives the movement of the vesicle along the microtubule at up to 5 μm/s.
