Chain A ( V500 S501 E503 A504 G505 F506 S507 Y508 S509 H510 A511 G512 S514 N515 R516 L517 A518 R519 D520 N521 E522 L523 R524 D527 D549 F550 W552 S553 H554 R555 H556 Y557 Q582 )