At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
At it's most basic, a PEST motif is a sequence within a protein which is rich in proline, glutamic acid, serine and threonine. This sequence is a target for ubiquination - when a protein is ubiquinated or 'tagged; for degradation - so it's a type of protein-protein interaction domain.
I can answer in more detail if that's not sufficient. :D
Can you explain to me what PEST stands for, and what type of tag is utilized?
We hard core protein biochemists refer to the individual amino acids so often that we abbreviate each with a letter. In this case P stands for proline, E stands for glutamic acid, S stands for serine and T stands for threonine. So in this case, the domains are simply named for the single letter abbreviations of the amino acids in which they are enriched. It could have been called a EPTS motif or a STEP motif (actually, STEP motif does seem like a cool name) but PEST must have seemed more memorable to the people who named it. The tag itself is a very small (just 76 residue - tiny) protein called ubiquitin. Ubiquitin is attached to target proteins (in their PEST domains) by other proteins - called ubiquitin ligases - and, once attached, it mediates the interaction between the target protein and other proteins which degrade or break down the target protein.
I have all 20 natural amino acids memorized and their structures and basic details I probably should have guessed but I'm still working towards becoming, a "hardcore" biochemist. Thanks for the explanation very informative.