Chain A ( R81 Y84 L85 Y87 K88 N89 G90 F94 P97 K204 R301 E304 A305 T306 V307 W308 I309 D310 A311 T313 Q314 F317 E377 A380 T381 E382 G383 A384 T470 D473 T474 F475 A477 G478 V535 S536 I537 I538 N539 F540 K541 P542 L543 T544 Y545 D546 D547 Y548 I549 F550 N555 W559 )