Final Answer:
COP-II (Coat Protein Complex II) travels in the anterograde direction, meaning it moves from the endoplasmic reticulum (ER) to the Golgi apparatus. The initiator/adaptor for COP-II is Arf1. So, the correct option is C. Anterograde; Arf1.
Step-by-step explanation:
The correct option is C. Anterograde; Arf1. COP-II, or Coat Protein Complex II, is a vital component in the intracellular transport of proteins. It functions in the anterograde direction, orchestrating the movement of vesicles from the endoplasmic reticulum (ER) to the Golgi apparatus within the cell. This directional transport is crucial for the secretory pathway, enabling the delivery of newly synthesized proteins to their intended destinations.
The initiator and adaptor for COP-II-mediated transport is Arf1 (ADP-ribosylation factor 1). Arf1 plays a pivotal role in the formation of COP-II-coated vesicles. As a small GTPase, Arf1 undergoes a cycle of GTP binding and hydrolysis, which regulates its activity in initiating vesicle formation. When Arf1 is in its GTP-bound state, it associates with the ER membrane and recruits the COP-II complex, initiating the budding of vesicles containing cargo proteins.
Understanding the specificity of the initiator/adaptor, Arf1, and the anterograde direction of COP-II transport sheds light on the finely tuned intracellular processes governing protein trafficking. This mechanism ensures the proper delivery of proteins synthesized in the ER to the Golgi apparatus, a fundamental step in cellular function and maintenance.