Chain A ( V125 I126 P129 L130 Y133 A206 V207 F208 I209 F210 K211 K212 K213 V214 G215 K216 P217 V218 A219 N221 L222 N225 H226 N227 L228 S229 H230 F231 L232 K233 Q235 K236 T239 Q240 I243 )