Transport · membrane bubbles
Vesicles & motor proteins
Delivery on rails
In view
A kinesin, slowed about 60× so you can follow it, walks hand-over-hand toward the microtubule’s plus end, burning one ATP per 8 nm step. Elsewhere, vesicles fuse with the membrane and release their cargo in small bursts.
Cargo travels between compartments in coated membrane bubbles 50–100 nm wide, or in larger tubes. Motor proteins haul them along microtubules: kinesin walks outward to the membrane, and dynein, switched on by dynactin and an adaptor, walks back toward the centre.
At the surface, secretory vesicles fuse and spill their contents outside (exocytosis). Clathrin-coated pits pinch inward to bring material in (endocytosis).
- Vesicle size
- 50–100 nm (coated)
- Kinesin step
- 8 nm · 1 ATP
- Top speed
- ≈ 0.8 µm/s
- Nobel
- 2013 · vesicle traffic
Did you know?
Kinesin’s two feet really take turns: the back one swings past the front one on every step. Single-molecule tracking confirmed this hand-over-hand walk in 2004.
Sources
- Kinesin Walks Hand-Over-Hand · Yildiz et al. 2004 · Science
- Kinesin hydrolyses one ATP per 8-nm step · Schnitzer & Block 1997 · Nature
- Direct observation of kinesin stepping by optical trapping interferometry · Svoboda et al. 1993 · Nature
- COPII-coated vesicles: flexible enough for large cargo? · Fromme & Schekman 2005 · Current Opinion in Cell Biology
- CALM regulates clathrin-coated vesicle size and maturation by directly sensing and driving membrane curvature · Miller et al. 2015 · Dev Cell
- Organellar relationships in the Golgi region of the pancreatic beta cell line, HIT-T15, visualized by high resolution electron tomography · Marsh et al. 2001 · Proc Natl Acad Sci U S A
- Correlative light-electron microscopy reveals the tubular-saccular ultrastructure of carriers operating between Golgi apparatus and plasma membrane · Polishchuk et al. 2000 · J Cell Biol
- Molecular Motors: Strategies to Get Along · Mallik & Gross 2004 · Current Biology
- Mechanism and regulation of cytoplasmic dynein · Cianfrocco et al. 2015 · Annu Rev Cell Dev Biol
- Activation of cytoplasmic dynein motility by dynactin-cargo adapter complexes · McKenney et al. 2014 · Science
- The cytoplasmic dynein transport machinery and its many cargoes · Reck-Peterson et al. 2018 · Nat Rev Mol Cell Biol
- The Nobel Prize in Physiology or Medicine 2013 · NobelPrize.org
- Mechanisms of clathrin-mediated endocytosis · Kaksonen & Roux 2018 · Nat Rev Mol Cell Biol
- How fast do molecular motors move on cytoskeletal filaments? · Milo & Phillips · Cell Biology by the Numbers