import re
s = """155 Phe 12xD,7xQ,5xE,5xG,4xA,4xS,2xF,2xH,2xI,2xK,1xM,1xN
151 Glu 11xD,6xA,5xE,3xF,3xG,3xM,2xI,2xS,1xH,1xK,1xL,1xP
159 Thr 15xF,6xL,6xM,5xG,5xI,5xT,4xA,4xV,3xR,1xD,1xN,1xP"""
print re.sub(r",?\b[0-5]x[a-zA-Z]\b","", s)
aW1wb3J0IHJlCnMgPSAiIiIxNTUgICAgUGhlICAxMnhELDd4USw1eEUsNXhHLDR4QSw0eFMsMnhGLDJ4SCwyeEksMnhLLDF4TSwxeE4KMTUxICAgIEdsdSAgMTF4RCw2eEEsNXhFLDN4RiwzeEcsM3hNLDJ4SSwyeFMsMXhILDF4SywxeEwsMXhQCjE1OSAgICBUaHIgIDE1eEYsNnhMLDZ4TSw1eEcsNXhJLDV4VCw0eEEsNHhWLDN4UiwxeEQsMXhOLDF4UCIiIgpwcmludCByZS5zdWIociIsP1xiWzAtNV14W2EtekEtWl1cYiIsIiIsIHMp