Chain A ( M463 T501 V502 F503 A504 S505 E506 L507 S508 V509 L512 C549 I568 L570 M572 I583 V584 F585 V586 L587 T588 L589 N590 I591 V592 A593 F594 V595 D633 C636 M637 A638 P639 I640 S641 F642 Y643 A644 L645 S646 I648 L662 L663 F666 Y667 N670 )