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NBME 23 Answers

nbme23/Block 1/Question#7
Which of the following is present in integral ...
Transmembrane region🔍

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submitted by step420(30),

Integral membrane proteins are found within the plasma membrane and span the whole length across. The inside of the membrane is very hydrophobic due to the long carbon chains. Extensive hydrophobic interactions between the protein side chain and the lipid tails will help anchor the protein in the membrane.

yb_26  O-linked glycosylation of secreted and membrane bound proteins is a post-translational event that takes place in the cis-Golgi compartment after N-glycosylation and folding of the protein +3  



 +1  upvote downvote
submitted by irgunner(2),

I was thinking signal sequence on the N-terminal end that would direct the protein into the RER to be then implanted into the plasma membrane. I guess transmembrane region is the better more specific answer?

drdoom  A bilayer has hydrophobic tails (polar head + nonpolar tails). If the N-terminus could be embedded in there, it would also have to be hydrophobic; but if an N-terminus were hydrophobic, it wouldn't dissolve well in the cytosol (=mostly water). In fact, an N-terminus probably wouldn't dissolve at all. If it were hydrophobic, it would aggregate with other, nearby N-terminuses (or other hydrophobic motifs). But if that happened, shuttle proteins couldn't recognize N-terminuses in the first place (they wouldn't be sterically accessible), nor deliver them to the rER. +  



 +0  upvote downvote
submitted by yb_26(147),

O-linked glycosylation of secreted and membrane bound proteins is a post-translational event that takes place in the cis-Golgi compartment after N-glycosylation and folding of the protein




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