Chain A ( K221 V222 T223 L224 L225 T228 E229 Y230 K239 G240 Q241 V242 L243 F244 D257 Y258 F259 G260 L261 L262 F263 Q264 E265 S266 P267 E268 Q269 K270 N271 W272 L273 D274 P275 A276 K277 E278 I279 Q282 L289 F290 T291 F292 N293 V294 K295 F296 Y297 P298 P299 D300 P301 F312 L313 C314 L315 Q316 L317 Q319 D320 R325 L326 L395 A398 K399 L401 S402 M403 Y404 G405 V406 D407 L408 H409 H410 A411 I419 K420 L421 G422 V423 C424 A425 N426 G427 L428 L429 I430 Y431 K432 D433 R434 L435 W442 I445 L446 K447 I448 S449 Y450 K451 R452 S453 N454 F455 Y456 I457 K458 T470 I471 G472 F473 L475 P476 N477 H478 R479 A480 A481 K482 R483 L484 W485 K486 V487 C488 V489 E490 H491 H492 T493 F494 Y495 R496 L497 V498 S499 P500 S513 F515 R516 Y517 S518 G519 R520 T521 Q522 I767 E772 E774 )