Chain A ( R69 S70 T71 P72 D73 G74 T75 H222 N223 C224 E225 Y238 M239 E240 M242 E252 G253 R254 M255 I397 K401 E403 E404 L406 R462 L463 D465 Q466 H467 R468 A469 R470 Q471 T473 L474 I753 V754 R755 N756 I757 L758 I759 D760 F761 T762 K763 G765 L766 L767 F768 R769 G770 R771 I772 S773 L776 F782 L787 Q789 I790 L797 V800 R801 A802 I803 L804 Q805 L809 E810 S811 T812 C813 D814 D815 S816 I817 I818 V819 K820 E821 V822 C823 )