Figure 1. The amino acid sequence of PV and its location in the carboxyl terminus of TRβ1 (A) and TRα1 (B). The PV mutation was identified in a patient with resistance to thyroid hormone. The mutation is from a C-insertion at codon 448 of TRβ1, resulting in a frame-shift mutation in the last 16 carboxyl terminal amino acids. The same PV mutation was targeted to the TRβ and TRα genes to create TRβPV and TRα1PV mice.