Chain A ( V54 L55 M56 H57 K58 T59 L60 R61 N62 P63 Y64 A65 I66 L67 A68 A69 Y141 S144 K145 I148 C149 R234 D235 L236 T237 Q238 F239 L240 K241 N242 Q243 K244 R245 Y246 Q305 D307 )