Chain A ( N64 F66 H67 K115 K116 I117 D118 N119 F120 L121 P155 I156 T158 K218 K219 L221 T223 D224 L225 T243 K244 A245 N246 P259 N260 V261 G262 M263 F264 K265 F432 S433 V434 I435 F437 H458 )