Fig. 3. Site 32 in (A) 2MP-α₃C and (B) 4MP-α₃C consist of atoms from hydrophobic amino acids (not shown) and five hydrophilic residues, K₁₇, K₂₉, K₃₆, E₁₃ and E₃₃. The phenol OH points toward (2MP-C₃₂) or away from (4MP-C₃₂) the carboxylate groups of E₁₃ and E₃₃. Analysis of the 2MP-α₃C structure provides a phenol O to glutamate O distance of 3.2 ± 0.5 Å and 7.2 ± 0.2 Å for the 2MP-C₃₂/E₁₃ and 2MP-C₃₂/E₃₃ pair, respectively.