Prolyl Isomerization as a Molecular Memory in the Allosteric Regulation of the Signal Adapter Protein c-CrkII |
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Authors: | Philipp A. M. Schmidpeter Franz X. Schmid |
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Affiliation: | From the Laboratorium für Biochemie und Bayreuther Zentrum für Molekulare Biowissenschaften, Universität Bayreuth, 95440 Bayreuth, Germany |
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Abstract: | c-CrkII is a central signal adapter protein. A domain opening/closing reaction between its N- and C-terminal Src homology 3 domains (SH3N and SH3C, respectively) controls signal propagation from upstream tyrosine kinases to downstream targets. In chicken but not in human c-CrkII, opening/closing is coupled with cis/trans isomerization at Pro-238 in SH3C. Here, we used advanced double-mixing experiments and kinetic simulations to uncover dynamic domain interactions in c-CrkII and to elucidate how they are linked with cis/trans isomerization and how this regulates substrate binding to SH3N. Pro-238 trans → cis isomerization is not a simple on/off switch but converts chicken c-CrkII from a high affinity to a low affinity form. We present a double-box model that describes c-CrkII as an allosteric system consisting of an open, high affinity R state and a closed, low affinity T state. Coupling of the T-R transition with an intrinsically slow prolyl isomerization provides c-CrkII with a kinetic memory and possibly functions as a molecular attenuator during signal transduction. |
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Keywords: | Adaptor Protein Allosteric Regulation Biophysics Protein Folding Src Homology 3 Domain (SH3 Domain) c-CrkII Native State Prolyl Isomerization Sequential Mixing Stopped Flow |
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