Chain A ( Q286 W287 R288 E289 K290 F291 L292 I293 T294 R324 T477 C480 D481 V482 P495 D496 V497 F498 I499 Q500 N501 G502 Y513 N514 G515 M516 E619 L640 N641 Y642 V655 C656 N657 S658 N659 K660 S681 D683 )