The KDEL signal sequence is required for retaining proteins within the ER lumen. Assume there is a protein named XY. XY is intended to function in the ER lumen. How does protein XY acquire the KDEL signal sequence? That is, where does the KDEL sequence come from?

A. It is added to the protein XY during protein synthesis.
B. It is added to the protein XY in the ER lumen.
C. It is part of protein XY's AA sequence.
D. The KDEL sequence exists in a different polypeptide that interacts and binds to protein XY.

surface mining destroys mountain tops, landscapes, forests and wildlife habitats. on top of that, it leads to soil erosion and destruction of agricultural land. the landscape changes can also disrupt river channels and streams, which leads to flooding. which, can destroy plant life and other animals as well.

explanation:

d) center of the mid-ocean ridge

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thrombocytopenia, which is a deficiency in blood platelets, can cause bleeding and bruising in the dermis similar to senile purpura. other possible causes include: exposure to ultraviolet rays and aging skin are common causes of senile purpura. senile purpura may also be a sign of collagen loss in the skin and bones.