GTC Biotherapeutics (fka GTCB)

[aslan2772]

Re: Atryn Glycosylation, NXS=>NXT

My appologies if this has already been addresed, I haven't yet caught up on the most recent posts.

Pre_clinical, I think all your points are valid, but you raise possible concerns in #'s 1-3 which are uncommon, worst-case scenarios, IMHO. The exception is point #4, which could be a more realistic concern that I had not thought of.

In particular, the consensus sequences for post-translational modification are well-conserved across species and cell types, so while the sugar content of a given glycosylation site may vary across species, the presumption that a consensus site will be glycosylated is, by definition, not a risky hypothesis. I spent a chunk of my graduate school career mapping out phosphorylation sequences, making point mutants, and studying the underlying signaling of this form of post-translational modification. I also have some experience with glycosylation, ubiquitination, and lipid modification. In my experience, the most interesting sites for post-translational modification are the non-consensus sequences, such as NXS, which tend to be more dynamically regulated in various cell types and species, and are often sensitive to the activation states of particular signaling cascades. That being said, when you change such a site to a consensus sequence, the site is usually (with exceptions of course) fully modified, across a broad range of eukaryotic species and cell types. Thus it makes sense that degree of glycosylation of N135 of antithrombin is variable across expression systems, but the other 3 major glycosylation sites, which are NXT sequences, are not. So, in the case of antithrombin glycosylation at N135, I still think producing fully glycosylated Atryn-"alpha" in goats milk would be a snap -- its just the sugar content of the glysosylation that is likely to be differ from the human form.