Chain A ( M1 E6 T9 N10 L13 Y63 L67 Y78 G89 S90 A93 A94 M96 K97 D143 L144 I147 S160 A161 F162 A163 C164 A166 S167 E168 G169 F170 R171 T172 W174 G175 M176 N178 M179 P237 G238 I240 N241 G242 C243 A244 Q245 R246 I247 S249 D250 F251 I252 K253 A254 L255 A256 F257 Y258 I259 Q260 L261 C262 A263 )