Chain A ( D238 S239 K240 T241 F242 L243 R258 I259 L262 T301 E318 Q320 C337 V338 N339 Y340 V341 V342 ),  Chain B ( R366 H367 N368 T374 F446 Q447 N448 P449 Y450 S451 D452 E453 I454 E455 Y456 I458 )