USMLE Location of glycosylation of hydroxylysine residues in collagen

[Geber]

Hi SDN fam.

Does anyone know what is the sub-cellular localization of glycosylation of hydroxylysine residues in collagen synthesis - rER or Golgi? And does anyone know if this is a type of O-linked or N-linked glycosylation?

Here's what I have so far:
- First Aid 2018 seems to suggest it happens in the rER
- USMLERx Qbank explanations state it happens in the Golgi (Rx video says ER!!!!!)
- My go-to reference book Lippincott Biochem Review is silent on it AFAIK
- From a quick search online it looks like it falls under the category of O-linked glycosylation. Does that mean it happens in the Golgi?

The emphasis on which step in collagen synthesis takes place where in the cell is pretty strong in some of the videos imo so not knowing this is driving me crazy lol

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[Agent Michael Scarn]

I read this and thought "man, who lets a tiny detail like that drive them crazy?"

30 minutes later, I got a Uworld question wrong about collagen synthesis. Flippity floppity, joke's on me.

Edit: Oh, and it happens in the ER, because I just learned that.

 

[Geber]

Haha just one of those things. Thanks! I think I'm content with the answer that it happens at both places but the USMLE wants you to learn that its in the rER majorly. Secondly, it's O-linked glycosylation (just not on threonine/serine).

Good luck to you!