Association and dissociation kinetics of colicin E3 and immunity protein 3: convergence of theory and experiment |
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Authors: | Zhou Huan-Xiang |
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Institution: | Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306, USA. zhou@sb.fsu.edu |
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Abstract: | The rapid binding of cytotoxic colicin E3 by its cognate immunity protein Im3 is essential in safeguarding the producing cell. The X-ray structure of the E3/Im3 complex shows that the Im3 molecule interfaces with both the C-terminal ribonuclease (RNase) domain and the N-terminal translocation domain of E3. The association and dissociation rates of the RNase domain and Im3 show drastically different sensitivities to ionic strength, as previously rationalized for electrostatically enhanced diffusion-limited protein-protein associations. Relative to binding to the RNase domain, binding to full-length E3 shows a comparable association rate but a significantly lower dissociation rate. This outcome is just what was anticipated by a theory for the binding of two linked domains to a protein. The E3/Im3 system thus provides a powerful paradigm for the interplay of theory and experiment. |
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Keywords: | Protein protein association ribonuclease colicin immunity protein electrostatic rate enhancement flexible linker |
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