Key Concepts Of Section 173

Vesicle Traffic in the Early Stages of the Secretory Pathway

■ COPII vesicles transport proteins from the rough ER to the cis-Golgi; COPI vesicles transport proteins in the reverse direction (see Figure 17-14).

■ COPII coats comprise three components: the small GTP-binding protein Sar1, a Sec23/Sec24 complex, and a Sec13/Sec31 complex.

■ Components of the COPII coat bind to membrane cargo proteins containing a di-acidic or other sorting signal in their cytosolic regions (see Figure 17-15). Soluble cargo proteins probably are targeted to COPII vesicles by binding to a membrane protein receptor.

■ Membrane proteins needed to form COPII vesicles can be retrieved from the cis-Golgi by COPI vesicles. One of the sorting signals that directs membrane proteins into COPI vesicles is a KKXX sequence, which binds to sub-units of the COPI coat.

■ Many soluble ER-resident proteins contain a KDEL sorting signal. Binding of this retrieval sequence to a specific receptor protein in the cis-Golgi membrane recruits missorted ER proteins into retrograde COPI vesicles (see Figure 17-16).

■ COPI vesicles also carry Golgi-resident proteins from later to earlier compartments in the Golgi stack.

■ Soluble and membrane proteins advance through the Golgi complex by cisternal progression, a nonvesicular process of anterograde transport.

Was this article helpful?

0 0
10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

Get My Free Ebook


Post a comment