A 21 nucleotide deletion encoding 7 C-terminal amino acids (the T site) was created in exon 16. An frt-flanked fragment containing a PKG-neo and a Tn5 promoter-driven chloramphenicol-acetyltransferase was inserted 1.6 kb downstream of deletion in exon 16. Western blot analysis confirmed expression is 76.3+/-3.0% of wild-type.