Thermodynamics of protein-protein interactions of cMyc, max, and mad: Effect of polyions on protein dimerization
Thermodynamics of protein-protein interactions of cMyc, max, and mad: Effect of polyions on protein dimerization
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DOI：
10.1021/bi0522551
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发表时间：
2006-02-21
期刊：
影响因子：
2.9
通讯作者：
Goss, DJ
中科院分区：
文献类型：
--
作者：
Banerjee, A;Hu, JZ;Goss, DJ
Myc-Max-Mad蛋白网络激活或抑制基因转录取决于Max的二聚化伴侣是c-Myc还是Mad。为了阐明这些蛋白质-蛋白质相互作用的物理性质，使用TRITC标记的Max的荧光各向异性。测定Max-Max同二聚体和c-Myc-Max和Mad-Max异二聚体的结合亲和力和二聚化热力学。我们的研究结果表明，c-Myc和Max形成最稳定的异源二聚体。先前的工作[科勒，J. J.，Metallo，S. J.，Schneider，T. L.，和Schepartz，A.（1999）Proc. Natl. Acad. Sci. U.S.A.96，11735-9]已经表明，这些蛋白质不是首先二聚化然后结合DNA，而是使用单体途径，其中单体结合DNA，然后在DNA表面上二聚化。DNA E-box影响二聚化，但非特异性效应也可能发挥作用。聚离子，聚-L-赖氨酸和聚-L-谷氨酸，的影响进行了研究，以确定带电的聚合物，而不是DNA对同源二聚化和异源二聚化的影响。虽然带正电荷的聚-L-赖氨酸PLL没有显示出任何显著的效果，但带负电荷的聚-L-谷氨酸PLG使异二聚体和同二聚体稳定2-3 kJ/mol。这些数据表明，在细胞核中，带负电荷的DNA或RNA的存在可以非特异性地帮助这些蛋白质的缔合。从K-d的温度依赖性计算Δ H度和Δ S度表明，尽管二聚体的热力学参数不同，但所有三种二聚体的反应都由负（有利）熵贡献和负（不利）熵贡献驱动。在PLG的存在下，熵变得更负，对于c-Myc-Max异二聚体的影响最大。这表明，货车范德华力和H-键的相互作用是占主导地位的这些蛋白质的二聚体。
The Myc-Max-Mad network of proteins activates or represses gene transcription depending on whether the dimerization partner of Max is c-Myc or Mad. To elucidate the physical properties of these protein-protein interactions, fluorescence anisotropy of TRITC-labeled Max was used. The binding affinities and thermodynamics of dimerization of the Max-Max homodimer and c-Myc-Max and Mad-Max heterodimers were determined. Our results indicate that c-Myc and Max form the most stable heterodimer. Previous work [Kohler, J. J., Metallo, S. J., Schneider, T. L., and Schepartz, A. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 11735-9] has shown that instead of dimerizing first and then binding to DNA, these proteins use a monomer pathway in which a monomer binds to DNA followed by dimerization on the surface of the DNA. The DNA E-box affects the dimerization, but nonspecific effects may also play a role. The influence of polyions, poly-L-lysine and poly-L-glutamic acid, were investigated to determine the effects of charged polymers other than DNA on homodimerization and heterodimerization. While the positively charged poly-L-lysine, PLL, did not show any significant effect, negatively charged poly-L-glutamic acid, PLG, stabilized both heterodimers and homodimers by 2-3 kJ/mol. These data suggest that in the cell nucleus the presence of negatively charged DNA or RNA could nonspecifically aid in association of these proteins. Calculations of Delta H degrees and Delta S degrees from the temperature dependence of K-d indicated that although the thermodynamic parameters for the dimer are different, the reactions for all three dimers are driven by negative (favorable) enthalpic and negative (unfavorable) entropic contributions. In the presence of PLG, entropy became more negative with the effect being largest for c-Myc-Max heterodimers. This suggests that van der Waals and H-bonding interactions are predominant in dimerization of these proteins.