Chain A ( R246 Q247 Q248 I249 A250 C251 G253 G254 P255 P256 T500 W501 D502 Q503 V504 A505 E506 V507 S509 W510 F512 S513 S514 T516 K517 R518 G519 L520 S521 I522 E523 Q524 L525 T526 T527 L528 A529 Y539 S540 G541 C542 Q543 W580 ),  Chain C ( V219 C220 T221 K222 H223 R224 R225 K226 G227 S228 H229 F234 Q235 R236 I247 Q248 R259 L260 H261 T262 )