(2S)-2-amino-3-phosphonooxy-propanoic acid

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Cryo-EM structures of PP2A:B55-FAM122A and PP2A:B55-ARPP19.

ARPP19 is a potent inhibitor of PP2A:B55, and increases affinity when phosphorylated.

GH are cloning artifacts.
residues S62 and S104 are phosphorylated.

cAMP-regulated phosphoprotein 19, 112 amino acids starting from "MSA",
S62 and S104 are phosphorylated.

Full length ARPP19, phosphorylated on S62 and S104