Anti-pY antibody pY20 prefers pY226 and pY243 over pY257 and pY282 of BTLA^INT. (A) Amino acid sequences of WT BTLA^INT and single Y mutants used for testing the preference of pY20. (B) IBs showing the preferences of pY20 among the four phosphorylatable tyrosine residues within BTLA^INT. Similar levels of purified His₁₀-BTLA^INT (YFFF), His₁₀-BTLA^INT (FYFF), His₁₀-BTLA^INT (FFYF), and His₁₀-BTLA^INT (FFFY) were loaded as indicated by anti-His IB.