Chain A ( L56 A60 M61 R62 K63 N64 H65 F66 N67 L70 M127 R131 Y132 V134 L135 K136 R137 S138 S139 T140 N149 L249 M252 L253 I254 E255 A256 R257 R259 S272 Q273 A274 E275 R276 T277 T278 M280 L281 C334 M337 S338 N339 V340 F341 R343 E381 I382 M383 A384 )