/usr/share/genometools/gtdata/trans/TransProt3B is in genometools-common 1.5.1-2ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | # 3-character charge alphabet
DE A
HKR C
ACFGILMNPQSTVWYJ N
XUBZO*-
|