Chain A ( L49 Y50 R51 Y52 G53 Y54 T55 R56 V57 A58 M60 R61 C99 G100 V101 P102 D103 L104 G105 R106 F107 Q108 T109 F110 D177 G178 Y179 P180 A191 F192 P193 E573 F580 L596 R599 D602 K603 L604 G605 L606 G622 K623 M624 R634 F635 D636 V637 K638 A639 Q640 M641 V642 D643 P644 S646 )