6. VEGF is synthetized in cancer cell to promote angiogenesis. Which sentence is

Question

6. VEGF is synthetized in cancer cell to promote angiogenesis. Which sentence is correct?

1.Polypeptide chain is synthetized on ribosomes attached to the ER (rough ER), and translocated through the membrane to the lumen by protein translocator, which is constantly active; mature VEGF chain is released to the lumen through signal peptidase cleavage.

2.Polypeptide chain is synthetized on ribosomes attached to the ER (rough ER), and translocated through the membrane to the lumen by protein translocator, which is activated by start-transfer sequence; mature VEGF chain is released to the lumen through signal peptidase cleavage.

3.Polypeptide chain is synthetized on ribosomes attached to the ER (rough ER), and translocated through the membrane to the lumen by protein translocator, which is activated by start-transfer sequence; mature VEGF chain remains embedded to the membrane for further transport

4.Polypeptide chain is synthetized on ribosomes attached to the ER (rough ER), and translocated through the membrane to the lumen by protein translocator, which is constantly active; mature VEGF chain remains embedded to the membrane for further transport

Explain the differences in mechanism of translocation in ER of secretory and plasma membrane receptors:

Explanation / Answer

The VEGF is the secretory protein which are synthesized on the rough ER. The ER signal sequence direct the ribosomes which synthesize these proteins to the rough ER. Then, these proteins are transported from RER to the secretory pathway by small vesicles that bud from the membrane of one organelle and then fuse with that of other. Correct answer is C.

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