Chain A ( W13 K14 R16 L17 N18 K22 F25 Q26 Y28 K29 K30 S31 G32 I33 Q34 E35 V36 R38 K42 S56 R57 G58 K61 F65 G148 E149 S150 S151 E157 R160 K181 L183 R207 N208 P209 L210 S211 R212 N213 S214 T215 H216 E217 Y219 L239 R242 F243 A250 Y252 )