![]() Cell signaling by receptor tyrosine kinases. A non-catalytic domain conserved among cytoplasmic protein-tyrosine kinases modifies the kinase function and transforming activity of Fujinami sarcoma virus P130gag-fps. As a result, several scaffold proteins have been identified as ultra-sensitive switches that toggle between opposing cellular processes. Three examples of this are the scaffolds that target phosphatases, those that control protein ubiquitylation and those that control acetylation and deacetylation.Ĭovalent modification of a scaffold protein can determine which binding partners are included in the complex and thus provide alternative functionality. Protein scaffolds can also be organized around signal termination enzymes that attenuate signalling or promote the degradation of key enzymes. AKAPs are dynamic participants in local signalling, in part owing to their flexibility in structure, transient interactions and combinatorial assembly of binding partners. Rather than functioning enzymatically, scaffolds formed by pseudokinases and pseudophosphatases can function as allosteric modulators of other signalling enzymes.Ī-kinase anchor proteins (AKAPs) constrain second-messenger-responsive enzymes, such as protein kinase A, in customized macromolecular units. They confer bidirectional control on cellular processes through the simultaneous recruitment of signal transduction and signal termination enzymes. Scaffold proteins are non-catalytic organizational elements that focus enzyme activity by holding members of a signal transduction cascade in place. ![]()
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