Thyroid hormone effect on rat heart mitochondrial proteins and affinity labeling with N-bromoacetyl-3,3',5-triiodo-L-thyronine. Lack of direct effect on the adenine nucleotide translocase.

N-bromoacetyl-3,3',5-tri[3'-125I]iodo-L-thyronine was used to label intact heart mitochondria from eu, hypo- and hyperthyroid rats in order to identify proteins involved in T3-regulated mitochondrial processes. The results show strong labeling, competed for by T3 and other analogues, of two proteins with a molecular mass of 48,000 and 49,200 Da. No labeling is seen of the adenine nucleotide translocase, a likely target, neither at 0 degree C, at room temperature, nor after preincubation with the substrates or specific inhibitors. No difference in labeling intensity or distribution is seen in mitochondria from eu-, hypo- or hyperthyroid rats, and the abundance of the adenine nucleotide translocase is unchanged, but five other proteins show differential abundance.