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I have seen the following question in a Cell Biology exam:

Which of the following is true"

  1. Insulin has an hydrophobic Signal Peptide and the insulin receptor does not have an hydrophobic Signal Peptide

  2. The insulin is coded by two genes, the insulin receptor has an hydrophobic sequence in the middle of the protein.

  3. Receptors in the ER bound the SRP that is bounded to the insulin receptor, SRP is made of RNA and proteins.

I think that (1) is the right answer. However, people I talked with thought (3) is the right one.

I think 1 is right because I have never seen anywhere that insulin receptor has a signal peptide so I assumed it does not have. I also think that SRP is a part of the insulin receptor, which is located on the ER (and not bounded to the ER by receptors), this is why I thought (3) is not the right answer.

Am I right, or did I miss anything?

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  • $\begingroup$ Eeeeh, if you meant insulin receptor has a signal peptide which is removed during receptor maturation, then you are correct. uniprot.org/uniprot/P06213 $\endgroup$ – Jeppe Nielsen Oct 22 '17 at 16:59
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Signal recognition particle (SRP) receptor, also called docking protein, is a dimer composed of 2 different subunits that are associated exclusively with the rough ER in mammalian cells. The surface of the rough endoplasmic reticulum (often abbreviated RER or Rough ER) (also called granular endoplasmic reticulum) is studded with protein-manufacturing ribosomes giving it a "rough" appearance. so i don't think (3) is the right statement. the insulin receptors is made up of two hormones, insulin and glucagon, are at the center of this signaling system. there is no such things as hydrophobic sequence in the middle of the protein i believe. also, Insulin is a peptide hormone produced by beta cells of the pancreatic islets and and insulin receptors doesn't have an hydrophobic signal peptide. so i think (1) is the correct answer. Edit : https://en.wikipedia.org/wiki/Signal_recognition_particle_receptor https://www.healthline.com/health/type-2-diabetes/insulin#Function1 www.news-medical.net/health/What-is-Insulin.aspx

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