Undocumented features

Prosite documents the PA line, which is a regular expression.

   pattern: G-{EDRKHPFYW}-x(2)-[STAGCN]-{P}.
   regexp:  G[^EDRKHPFYW].{2}[STAGCN][^P]
                           - Tisdall's perl.com article

Here's Python code for the translation

_prosite_trans = string.maketrans("abcdefghijklmnopqrstuvwxyzX}()<>",
                                  "ABCDEFGHIJKLMNOPQRSTUVW.YZ.]{}^$")
def prosite_to_re(pattern):
    s = string.replace(pattern, "{", "[^")
    s = string.translate(s, _prosite_trans, "-.")
    return s