Chain A ( V22 Y81 D82 R85 E88 Y89 N282 K308 P309 A310 D311 K314 G315 ),  Chain B ( L370 L371 S372 S373 K374 S375 G376 F377 W378 G391 T392 Y393 P394 Q395 T396 F433 E435 C436 A437 )