Chain A ( M518 S519 V520 Y525 K529 Q530 I531 G532 S533 G534 G535 S536 S537 K538 V539 F540 Q541 V542 Y550 A551 I552 K553 Y554 V555 N556 L557 A560 D561 T564 L565 D566 S567 Y568 R569 N570 E571 I572 Y574 L575 I585 I586 R587 E592 I593 T594 Y597 I598 Y599 M600 V601 M602 E603 C604 G605 H645 D647 K649 A651 N652 I663 D664 F665 G666 I667 A668 N669 Q670 )