Chain A ( Y11 V63 V64 S66 L67 N70 S87 L90 E91 R94 T95 L98 Y169 R175 I178 G243 W244 P246 A247 L250 Y251 I252 L253 T254 A255 N269 I270 F271 A272 L273 T275 L276 I279 M280 )