In vitro triiodothyronine binding to non-histone proteins from rat liver nuclei |
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Authors: | P Thomopoulos B Dastugue N Defer |
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Affiliation: | 1. Unité de Recherches sur le Métabolisme des Lipides, U. 35, I.N.S.E.R.M. France;2. Institut de Pathologie Moléculaire. Faculté de Médecine Cochin, 75014 - Paris, France |
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Abstract: | incubations of non-histone proteins from rat liver nuclei with labelled L-3, 5, 3′ triiodothyronine demonstrate the existence of high affinity, limited capacity binding sites for the hormone in this protein group; the affinity was found identical for triiodothyroacetic acid and lower for L-thyroxine. Binding ability was highly temperature dependent. At 4°C, the rate constant of association was 0.9 × 107 M?1 h?1 and the rate constant of dissociation was 0.015 h?1. The dissociation constant Kd was calculated from these data or measured by Scatchard analysis and found to be between 1.6 and 5 × 10?9 M. The maximum binding capacity was 10?13 moles of L-3, 5, 3′ triiodothyronine per 100 μg non-histone proteins or 6000 hormone molecules per nucleus. Protein binding had a half-life of 20 hours at 4°C, in the absence of hormone, but was found to be very stable in the presence of hormone. |
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Keywords: | NHP non-histone nuclear proteins L-thyroxine L-T3 L-3 5 3′ triiodothyronine L-3 5 diiodothyronine triac 3 5 3′ triiodothyroacetic acid MIT L-monoiodotyrosine DIT L-diiodotyrosine |
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