Figure 5.

Detailed view of the exposed Arg^P315 and its interactions with B4e8. Hydrogen bonds and salt bridges are shown by dashed lines. Color coding is as in Fig. 4. Arg^P315 is sandwiched between Phe^P317 and Tyr^L32 and stabilized by a salt bridge and a hydrogen bond to the side chain and backbone of Asp^L92. The unusual α-turn conformation is stabilized by two hydrogen bonds between Asn^H100d and the backbone of Arg^P315 and Pro^P313, respectively.