Chain A ( V49 D50 C51 T52 D53 K54 H55 N69 L70 T71 L72 T73 I74 N75 F85 E93 I94 D95 F96 R97 C98 N99 C100 V101 L105 G106 S107 N110 F123 S131 L132 Y133 L134 D135 G136 N137 L153 S154 E156 L177 Y178 Q181 R186 Y471 A472 R473 S474 C475 )