Conformational transition of thyroid hormone receptor upon hormone binding: demonstration by aqueous two-phase partitioning

• DOI: 10.1677/joe.0.1190431
• Publication Date: 2008-12-11T22:52:58Z
• Authors: K. Ichikawa; K. Hashizume; T. Miyamoto; Y. Nishii; K. Yamauchi; H. Ohtsuka; T. Yamada
• Keywords: Thyroid hormone receptor

An aqueous two-phase partitioning study of partially purified nuclear thyroid hormone receptor from rat liver was performed. Stability 3,5,3'-tri-iodo-L-thyronine (T3)-receptor complex and T3-binding activity in the presence dextran or polyethylene glycol were assessed order to determine amount occupied unoccupied receptors each phase. Partition coefficients calculated as ratio concentration upper glycol-rich phase H2O that lower dextran-rich H2O. The partition coefficient a sensitive function salt at pH above 6.1 below 5.1. had no effect on around 5.6. These results suggest isoelectric point is about 5.6, confirming previous determinations using focusing. decreased upon T3 binding, regardless composition. In contrast, thyroxine-binding globulin increased binding. Free preferentially partitioned into gave higher than 1.0. strongly decrease binding reflects conformational changes electrostatic properties Such an alteration may be involved biological activation