Tissue-dependent and developmentally regulated cytosolic thyroid-hormone-binding proteins (CTBPs) in Xenopus.
Xenopus cytosolic thyroid-hormone-binding proteins (CTBPs) were examined by a photoaffinity labeling and [125I]T3-binding assay. An affinity-labeled protein of 59 kDa, which was responsible for the major T3-binding activity in adult tissues, was predominant in liver. The 59-kDa CTBP first appeared in significant amounts at the metamorphic climax stage in liver cytosol and continued to be expressed after metamorphosis. Another affinity-labeled CTBP of 38 kDa appeared at the metamorphic climax stage in cytosol from head region, but disappeared after this stage. T3-binding assay using whole cytosol showed that a distinct CTBP, although not photoaffinity-labeled, was present in cytosol from hindlimb bud and gradually disappeared as the hindlimb grew. The cytosol from liver, head region, and hindlimb bud contained high affinity binding sites for T3 with Kd values ranging from 10(-9) to 10(-8) M. These results suggest that there are at least three distinct CTBPs in Xenopus cytosol, which are expressed in a tissue-dependent and developmentally regulated manner.
Yamauchi
K
K
Department of Biology, Faculty of Science, Shizuoka University, Japan. yamauchi@sci.shizuoka.ac.jp
Tata
J R
JR
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D005260:Female; D008675:Metamorphosis, Biological; D009928:Organ Specificity; D019920:Photoaffinity Labels; D014284:Triiodothyronine / Q000378:metabolism*; D014982:Xenopus laevis / Q000254:growth & development / Q000378:metabolism*
D002352:Carrier Proteins; D019920:Photoaffinity Labels; D014284:Triiodothyronine