biochem q on protein sequencing plz help

[sadaca]

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hey guys, what do u think of this q? I am very confused on the process of proteins coming from cytosol going to RER then golgi ? Could someone plz explain this in simple terms?
options are : 1) GOLGI, 2) ER 3) CYTOSOL 4) ENDOSOMES


I would greatly appreciate it.

 

[Miracoli]

3) CYTOSOL
Proteins destinated to RER then to golgi then to be secreted or to lysosome have a short hydrophobic SIGNAL PEPTIDE (5-30 aminoacids long) at the N-terminus. This is also called ER signal sequence and directs proteins to enter the endoplasmic reticulum (ER). The signal sequence binds to the SIGNAL RECOGNITION PARTICLE (SRP) which then binds to its receptor in RER, the SRP receptor. At the end, the signal peptide is cleaved off by SIGNAL PEPTIDASE

 

[sadaca]

hey friend, yep thats exactly what the explanation says. But I still dont' see how the cytosol is part of all of this? When would the answer be ER?

thanks alot

 

[sadaca]

hmm it says you attached a file to this, but I cannot see it.

 

[Miracoli]

I have not read what the explanation says🙂 If the ribosome with the protein can not got RER then the protein will be synthesized in the cytosol i.e. the ribosome with the protein stays in cytosol.

 

[sadaca]

hey friend,. That makes sense
thanks alot appreciate it

 

[dyspareunia]

I have not read what the explanation says🙂 If the ribosome with the protein can not got RER then the protein will be synthesized in the cytosol i.e. the ribosome with the protein stays in cytosol.
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But the question says PROhormone (not PREprohormone) meaning the signal peptide has already been cleaved off. Meaning it's already being translated on the ER.

 

[Miracoli]

But the question says PROhormone (not PREprohormone) meaning the signal peptide has already been cleaved off. Meaning it's already being translated on the ER.

Some proteins have only one signal peptide so are you still gonna call them PREprohormone or just PROhormone? Anyway Sadaca has the definitive answer, lets wait.

 

[sadaca]

hey guys, so it really doesn't go into that much details. Miracoli nailed the explanation home. But here it is so you can be sure. Its attached.

 

[Miracoli]

@sadaca, thanks!

 

[DeeJay2728]

Even without knowing the sequences, we should be able to figure out that deleting a proteins hydrophobic region is decreasing its lipophilicity, which means it's decreasing its ability to cross membranes, so it accumulates in the cytosol.