Chain A ( V253 M254 D255 A256 K289 I341 A342 G343 G344 L345 V346 C367 T368 E369 E370 V371 F372 Y385 F409 E410 S478 S479 A480 L481 Q482 R483 H517 R518 I519 A520 S521 Q522 L526 K531 P532 G533 V534 L548 G549 A550 D551 G552 G553 C554 P686 P687 Q688 D693 F694 M696 T697 D698 R702 )