Chain A ( S68 V69 V70 G71 F72 A73 V74 D75 L76 A77 N78 F110 E113 G149 Y152 N153 L248 V256 V262 T266 P270 Y271 Q314 F316 F317 S318 L319 G320 A321 F323 G324 V325 L326 F329 T346 A414 L415 G416 L417 D418 S419 S420 M421 G422 G423 M424 E425 A426 V427 )