Chain A ( F20 M23 H65 T68 R69 H73 R101 A102 P103 V104 S105 L106 T107 S108 N109 L110 N111 P112 Y155 I158 Y159 Y172 I174 A175 T176 T177 N178 A179 V182 A183 M185 L186 Y189 Y249 F252 L253 Y256 L257 A259 L260 Y263 Y264 F270 L272 R273 N274 A275 I276 F277 L278 E279 S280 V281 Q282 Q283 T284 P285 I286 )