Chain A ( F565 I566 S567 Y568 R569 R570 N571 S572 G573 S574 Q575 L576 A577 D594 V595 L598 F603 L607 F617 V618 L619 V620 S622 P623 G624 A625 L626 D627 K628 C629 K636 D637 W638 V639 H640 E642 I643 ),  Chain B ( H685 E686 )