Chain A ( Y545 K589 D590 E591 F592 E593 H594 K595 R596 K597 E598 L599 E600 Q601 C603 N604 ),  Chain B ( S432 D433 N434 P468 R469 F547 N548 M549 K550 S551 A552 V553 E554 D555 E556 L558 I562 K567 V570 L571 D572 )