Transport · membranski mehurići

Vezikule i motorni proteini

Dostava po šinama

U kadru

Kinezin, usporen oko 60× da biste mogli da ga pratite, hoda ruku preko ruke ka plus-kraju mikrotubule i troši jedan ATP za svaki korak od 8 nm. Na drugim mestima vezikule se stapaju s membranom i oslobađaju teret u malim naletima.

Teret putuje između odeljaka u obloženim membranskim mehurićima širokim 50–100 nm ili u većim cevima. Motorni proteini ih vuku duž mikrotubula: kinezin hoda ka spolja, do membrane, a dinein, koji uključuju dinaktin i adapter, hoda nazad ka centru.

Na površini se sekretorne vezikule stapaju s membranom i izbacuju sadržaj napolje (egzocitoza). Udubljenja obložena klatrinom uvlače se unutra i unose materijal (endocitoza).

Veličina vezikule

50–100 nm (obložene)

Korak kinezina

8 nm · 1 ATP

Najveća brzina

≈ 0,8 µm/s

Nobelova nagrada

2013 · promet vezikula

Da li ste znali?

Dva stopala kinezina zaista se smenjuju: zadnje pri svakom koraku prelazi preko prednjeg. Praćenje pojedinačnih molekula potvrdilo je taj hod 2004. godine.

Izvori

1. Kinesin Walks Hand-Over-Hand · Yildiz et al. 2004 · Science
2. Kinesin hydrolyses one ATP per 8-nm step · Schnitzer & Block 1997 · Nature
3. Direct observation of kinesin stepping by optical trapping interferometry · Svoboda et al. 1993 · Nature
4. COPII-coated vesicles: flexible enough for large cargo? · Fromme & Schekman 2005 · Current Opinion in Cell Biology
5. CALM regulates clathrin-coated vesicle size and maturation by directly sensing and driving membrane curvature · Miller et al. 2015 · Dev Cell
6. 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
7. 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
8. Molecular Motors: Strategies to Get Along · Mallik & Gross 2004 · Current Biology
9. Mechanism and regulation of cytoplasmic dynein · Cianfrocco et al. 2015 · Annu Rev Cell Dev Biol
10. Activation of cytoplasmic dynein motility by dynactin-cargo adapter complexes · McKenney et al. 2014 · Science
11. The cytoplasmic dynein transport machinery and its many cargoes · Reck-Peterson et al. 2018 · Nat Rev Mol Cell Biol
12. The Nobel Prize in Physiology or Medicine 2013 · NobelPrize.org
13. Mechanisms of clathrin-mediated endocytosis · Kaksonen & Roux 2018 · Nat Rev Mol Cell Biol
14. How fast do molecular motors move on cytoskeletal filaments? · Milo & Phillips · Cell Biology by the Numbers