Chain A ( Y204 N205 R206 I207 L208 E248 K251 S252 F254 S255 Y256 L268 Y269 H270 L271 E272 N273 N274 Y275 Y276 C277 N278 L279 D280 Y281 L282 S283 K303 N304 I305 L306 L307 Y308 K309 P310 K311 E312 N313 C314 F334 S676 P677 V678 M679 L680 P681 T682 K683 K684 R685 K686 K687 R688 V689 K690 V691 A692 K693 T694 L695 S696 S698 L715 L718 V719 N720 E721 L722 N723 E736 D738 )