Chain A ( L2 V6 D7 G8 E9 T10 C11 H12 D13 L14 F15 L16 L17 M18 G19 K20 V50 A51 A52 G53 F54 D55 K56 N57 V59 C60 I64 E73 V74 G75 T76 I90 F91 R92 I99 I100 N101 C103 F105 N106 N107 S138 N174 K245 T275 G291 V292 S293 G294 S321 G322 G323 L343 Y344 S345 C346 L347 V348 F349 G351 M352 )