Chain A ( I249 A250 C251 I252 G253 G254 M329 H332 P333 D334 R335 P336 V338 K340 T433 I464 I467 Q469 M470 P471 N472 A473 W474 A475 L478 Q503 V504 A505 E506 V507 L508 S509 W510 Q511 F512 S513 S514 T515 T516 K517 R518 L520 Q524 F549 C550 W562 V563 L565 D566 N567 I568 I569 D570 L571 V572 K573 K574 W580 F610 E616 G617 K642 )