Fig. 3

Phe57 in the P2 crystal structure. a The location and interactions of Phe57 in wt-P2. Note the C-H...π bonds on both faces of the Phe57 side chain. b Conformational effects of the F57A mutation (stereo view). Superposed are wt-P2 (magenta) and all individual P2-F57A monomers from the three crystal forms (6 in total). Note the apparent flexibility of helix α2 and the β3-β4 loop. c Discontinuity of the β barrel of P2; a line of water molecules mediates contact between strands β4 and β5