[Biopython-dev] selenocysteines

[Andrew Dalke]

Looks like U for selenocysteines is the right thing to do, so I
added that to the extended protein alphabet.  That also allowed
me to add 'X' as the symbol for unknown protein.

Anything which uses X for selenocysteines should translate it
to U on import.

SWISS-PROT is using 'C' + /translation comment for selenocysteines.
Since 'C' != 'X' it doesn't fall under that previous paragraph. :)

                    Andrew