Thursday, November 9, 2023

Great. Sulfo-Tyrosines are important? Here's how you detect them!

 I think the picture above encapsulates the problem pretty well, right? There is a 0.01something difference in mass between a phospho- and sulfo-tyrosine.

Better to just ignore that either of those are things and move on, right? Unfortunately, a this new paper points out, the sulfome is important in viral infections and even knocking out sulfo-transferases in mice makes them skinny and have poor vision....

...and we don't have any idea what the real breadth of the sulfome is. How many proteins get "sulfomed" (sulfo-ded?).

Until now! 

There is a lot in this paper. But they basically work out a modified IMAC that can preferentially enrich peptides with sulfated tyrosine residues using acetic acid to charge them and titanium or zirconium IMAC enrichment (go acetic acid!) 

Also - even ignoring the sulfonation stuff - how cool is it to be able to enrich modified tyrosine peptides without one of those awful anti-phosphoY antibodies. I haven't done it in a while, but incubating in a cold room overnight while a mixture of antibody rocks is not my idea of a good time. Zirconium and vinegar? Sign me up (plus the antibody is expensive and I've heard hasn't improved much in the last dozen years). Okay, on a re-read I think I'm not getting this right. Maybe it is only enriching the sulfo-Y. In which case I think I'll just study sulfo-Ys next time. 

Cool - so now they have peptides with modified tyrosines - how do you tell a 0.01something Da mod apart? On my instruments you don't. Particularly on a week like this one where we don't have heat in our building. My TOFs are like +/- 0.03something, though they seem a little better between 1 and 4pm. 

At very low collision energies, they neutral loss different! They use an NCE of 10 and that is enough to neutral loss sulfoY but not phosphoY! Then they can fragment it again with HCD or ETD or ETHCD or whatever. 

End result? MASSIVE improvement in our understanding of what proteins get Y sulfo-ed! What a cool resource for people out there who are into sulfo- metabolism and have (rightly) thought that mass spectrometrists can't really help them!

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