Chain A ( K199 I201 Q202 I203 W204 K205 R206 Q207 Q208 Q209 L210 A211 N213 F217 Q281 I426 L427 W428 D429 N430 A431 F432 S433 E434 M435 D436 R437 V438 F440 V441 V442 A443 V446 P447 K450 M451 E453 T454 )