Phosphorylation signal is very weak protein visualized – protein interactions.

 

Wuhan Institute of Physics and Mathematics, Tang Chun research group in collaboration with Zhejiang University School of Medicine, Associate Professor Zhang Wei Ping, the use of new technologies, successfully obtained KD ≈ 25 mM protein interaction complex structures.

Phosphorylation signal is very weak protein visualized - protein interactions

Icon: between bacterial phosphotransferase system (PTS) of the two proteins EI and EIIAGlc through very weak interactions, forming a transient interaction complexes, the phosphate group can be passed directly to EI EIIAGlc. Interaction composite structure showed two proteins interact through hydrophobic interactions, since the interface between the two proteins are negatively charged, resulting in a very weak interaction.

Wuhan Institute of Physics and Mathematics, Tang Chun research group in collaboration with Zhejiang University School of Medicine, Associate Professor Zhang Wei Ping, the use of new technologies, successfully obtained KD ≈ 25 mM protein interaction complex structures. This proves not only between very weak intracellular signaling protein interactions, also proposed the existence of a very weak interaction of significance for the protein – as well as studies of cell signaling protein interaction provides a new method to open the new horizons. Relevant outcomes published in “Angewandte Chemie” magazine, was chosen hotspot article (hot paper), was recommended as cover story.

In the cell signaling process, the signal is passed through the interaction between proteins, such as the transfer of phosphate groups. However, the strength of the great differences in protein interactions, dissociation constants (KD) interaction in 1 nM or less, known as stable interaction, 1 nM – 1 mM interactions between, known as transient interaction. Due to the lack of research methods, KD> 1 mM composite structure interaction is difficult to resolve, KD interactions 1-5 mM, the international community has only a few reports. Currently, the study of protein structure and function of the weak interaction has gradually become a hot international research. More and more evidence that the weak interaction is widespread and has important biological functions. Then, weak interaction can be detected how much, in a very weak protein – protein interactions, and it still has the biological function of?

Nuclear magnetic resonance (NMR) is the main method study of weak interactions between proteins, but protein complex interaction limit classical methods such as NOE, RDC and the conventional method of paramagnetic relaxation enhancement study for KD <10 mM of compound body. In the present study, Tang Chun research group developed a novel sensitive and long-range paramagnetic relaxation enhancement methods, based on the introduction of lanthanide Gd3 +, and extremely rigid paramagnetic probe, which greatly enhance the detection sensitivity, ultimately successfully obtained KD ≈ 25 mM protein interaction complex structures. By molecular dynamics simulations and found that the presence of complex time <1 ms, the authors of this very weak, there is a very short time interaction, named fleeting interaction. Structural analysis further been found that due to the interaction of the presence of a very weak hydrophobic interaction so that interaction between the two, but because of the interaction of the interface with the same negative result of charge repulsion.

These very weakly interacting complex of two proteins is E. coli phosphotransferase system of EI and EIIAGlc protein, phosphate groups can be passed between them. In general, increasing the concentration of intracellular signaling proteins (local concentration of many proteins may be up to about 10 mM), then the signal transmission speed. Simulation study authors found that when the protein concentration exceeds 1 mM, then matching KD must be greater than 1 mM, otherwise it will cause signal transmission “congestion”, the signal protein concentration increased to give the “dividend” disappeared.

This work is another important achievement of the interdisciplinary Wuhan achieved several things, not only to prove the existence of a very weak interaction between the intracellular signaling protein, also proposed the existence of a very weak interaction significance, protein – protein interaction studies and cell signaling research provides a new way to open up new horizons.

This work was supported by the Fund’s Ministry of Science, the National Natural Science Foundation of China, and the United States, Howard Hughes Medical Institute (

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