Indicate whether each of the following descriptions better applies to COPI- (1), COPII- (2), or clathrin- (3) coated vesicles. Y
our answer would be a four-digit number composed of digits 1 to 3 only, e.g. 1322. (1) They are uncoated by an hsp70 family protein, which is stimulated by the binding of auxilin.
(2) They keep their coat proteins for a relatively long time, until they dock onto their target membrane.
(3) Their uncoating depends on activation of an ARF-GAP.
(4) Their uncoating depends in part on activation of a Sar1-GAP.
Transport vesicles are vesicles that function to carry molecules from one cellular compartment to another. The coat protein complexes I and II (COPI and COPII) are conserved pathways that transport proteins from the endoplasmic reticulum to the Golgi apparatus. Moreover, clathrin is a protein implicated in the formation of coated vesicles. The ADP-ribosylation factor GTPase activating (Arf GAP) proteins play a major role in Arf signaling pathways, which are responsible for uncoating of the COPI coat. On the other hand, COPII vesicles are known to retain their coats until they are recognized by tethering complexes, and whose formation is regulated by the GDP-GTP cycle of the small GTPase Sar1. Finally, the 70-kDa heat shock proteins (HSP70) are chaperones which function as uncoating ATPases to remove clathrin from coated vesicles after endocytosis.
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