[ccp4bb]: Ions in the internal protein cavities - addendum 3

[Petr Leiman <leiman@purdue.edu>]

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I do not think that it is impossible for an ion to occupy a well suited
cavity in a protein that is folded to carry something in that cavity.
Like hemoglobin.
In the case we are talking about there is an elongated trimeric molecule
formed by intertwined polypeptide chains with mostly hydrophobic filling
and there is a plane of 3 Asps pointing to the axis surrounded by
hydrophobics. It is possible that an ion migrated along the axis of the
trimer but HOW on earth the protein folded so, that it had a
non-neutralized +3 charge inside and waited till we start to crystallize
it to suck something from the crystallization solution?

Petr