Chain A ( I53 H54 T55 L56 E57 H58 F60 A61 R65 I75 I76 D77 I78 S79 P80 F87 I120 P121 E122 L123 N124 Y126 Q127 C128 G129 ),  Chain B ( S6 F7 A8 V9 D10 H11 T12 M14 R20 A22 K23 V35 R39 S79 P80 M81 G82 C83 R84 T85 F87 Y88 S90 )