Chain A ( M22 S23 R24 V53 C54 L55 H56 F57 P111 V112 H113 I114 C115 G175 N176 V177 N178 W180 L184 I189 I192 Y193 L194 G195 G196 F198 S199 N204 W205 R206 A207 Q221 W223 P224 )