Chain A ( S754 F755 P756 A757 S758 L759 V760 V761 A762 P778 K779 Q954 L956 R957 A958 ),  Chain B ( D606 A607 C608 T609 K612 D647 T648 G649 A652 V653 N654 C655 T656 Y657 K658 C663 V664 V665 R666 F667 Q668 Y669 Y670 )