Functional properties of human thyroid hormone receptor beta 1 overexpressed using baculovirus

We have overexpressed the human beta 1 thyroid hormone receptor in insect cells using a recombinant baculovirus to a level of 5-10% of total cellular protein. The recombinant protein migrates as a 50 kDa band by SDS-PAGE and Western blot analysis. The expressed receptor binds to L-T3 with a Kd of 1.3 +/- 0.4 x 10(-10) M and to thyroid hormone analogues with an affinity hierarchy of TRIAC greater than L-T3 greater than L-T4 greater than rT3. Gel retardation assays show highly specific receptor binding to a TRE which is modified by the presence of ligand and avidin-biotin complex DNA analysis shows a Kd of 6.2 +/- 2.0 x 10(-10) M for this interaction. These results indicate high level expression of hTR beta with authentic hormone and DNA binding properties.