Purification of the mitochondrial triiodothyronine (T3) receptor from rat liver

The thyroid hormone receptor of the inner membrane of rat liver mitochondria was purified by osmotic and freeze-thaw lyses followed by partial purification on Sephadex G-200, and then by affinity chromatography with T3-Sepharose 4B. A single predominant protein band demonstrable on sodium dodecylsulphate (SDS) polyacrylamide gel electrophoresis was present in the first 4 mM NaOH elution peak of affinity chromatography. This was collected from affinity peaks from about 30 rat livers followed by preparative polyacrylamide gel electrophoresis. A single absorbance peak was observed by high pressure liquid chromatography (HPLC). The purified protein was analyzed for binding constants, amino acid composition, and characterized by analytical ultracentrifugation. The association constant (KA) exceeded 10(11) M-1. The sedimentation coefficient (S20,W) was 2.2S, partial specific volume (v) 0.72, frictional coefficient (f/fo)s M 1.68 and the molecular weight was estimated at 28 000. The amino acid composition was obtained.