Chain A ( Y231 D255 S257 P267 R296 L297 H298 E318 L319 D320 S322 Q344 L345 D346 L372 K373 I374 L375 R376 R378 L399 E400 V401 L402 D403 V425 D427 S429 P457 Q458 V459 L460 E461 Q462 L463 H464 Y465 F466 R467 D469 K470 Y471 K480 E481 A482 S483 F484 M485 S486 V487 N488 E489 S490 C491 Y492 D499 S501 K502 N523 S525 D548 K600 )