Brtko J, Knopp J
Institute of Experimental Endocrinology, Centre of Physiological Sciences, Bratislava, Czechoslovakia.
Acta Endocrinol (Copenh). 1988 Feb;117(2):159-65. doi: 10.1530/acta.0.1170159.
The role of histidyl, tyrosyl, alpha-or epsilon-amino residues of rat liver nuclear receptors for the specific binding of T3 was studied by chemically modifying the receptor molecule. The kinetics of the formation of N-carbethoxyhistidyl derivative from histidyl groups of nuclear receptors by diethylpyrocarbonate was examined. The modified nuclear receptor fraction was separated from diethylpyrocarbonate by gel filtration and the T3 binding parameters (Ka and MBC) at pH 8.0 were tested by Scatchard plot analysis. At 0.1 mmol/l diethypyrocarbonate, the value of Ka was significantly (P less than 0.01) decreased without any change in maximal binding capacity (MBC). The modification of alpha- or epsilon-amino groups of nuclear receptors by excess of trinitrobenzenesulfonic acid, 6.3 mmol/l at pH 8.5, resulted in a 4-fold increase in MBC of T3 specific binding without any change in Ka. In addition, acetylation of tyrosyl residues of nuclear receptors at pH 7.5 with an excess of 24 mmol/l N-acetylimidazole was performed. No changes in nuclear receptor Ka or MBC were observed after N-acetylimidazole treatment. Histidine and/or amino groups of the receptor molecule seem to hold a key position in the generation of the biologically active T3-nuclear receptor complex in the rat liver.
通过化学修饰受体分子，研究了大鼠肝细胞核受体中组氨酸、酪氨酸、α-或ε-氨基残基在三碘甲状腺原氨酸（T3）特异性结合中的作用。检测了焦碳酸二乙酯使核受体组氨酸基团形成N-乙氧羰基组氨酸衍生物的动力学过程。通过凝胶过滤将修饰后的核受体组分与焦碳酸二乙酯分离，并通过Scatchard作图分析测定pH 8.0时的T3结合参数（Ka和最大结合容量[MBC]）。在0.1 mmol/L焦碳酸二乙酯存在下，Ka值显著降低（P<0.01），而最大结合容量无变化。在pH 8.5时用6.3 mmol/L过量的三硝基苯磺酸修饰核受体的α-或ε-氨基，导致T3特异性结合的MBC增加4倍，而Ka无变化。此外，在pH 7.5时用24 mmol/L过量的N-乙酰咪唑对核受体的酪氨酸残基进行乙酰化。N-乙酰咪唑处理后未观察到核受体Ka或MBC的变化。受体分子的组氨酸和/或氨基似乎在大鼠肝脏中生物活性T3-核受体复合物的形成中起关键作用。
