Tyr 327 has alternate atoms. That means that in some crystal cells it sits
in the one position and in other crystal cells it sits in the other. As all
cells will be averaged by the X-ray experiment, we end up with one tyrosine
with two side chains (both with a fractional occupancy, of course).
(In docking we need to know which residues can easily adopt another side chain conformation (rotamer). If a side-chain already can have two rotamers in one crystal, then it can also easily move from one rotamer to the other if a ligand is around).