Protein scaffold meaning12/31/2023 membrane anchoring) ( 8, 13, 14), they can insulate MAPK signaling proteins from competing inputs, such as components from functionally distinct MAPK pathways ( 15, 16), and they are required for efficient signaling ( 17, 18). 1B) ( 5, 7, 8), they control MAPK pathway localization (e.g. ![]() The Ste5 and KSR scaffold proteins both carry out a similar set of functions: they physically assemble the individual kinases that make up their cognate MAPK cascades (as well as upstream regulators) ( Fig. 1B) both coordinate mitogen-activated protein kinase (MAPK) pathways, but do not appear to be related in sequence. For example, the Ste5 protein in yeast and the kinase suppressor of Ras (KSR) protein in mammals ( Fig. There are a number of examples of convergent scaffold evolution. Thus, scaffold proteins are flexible platforms assembled through mixing and matching of interaction domains. However, the other domains in individual AKAPs are highly variable, depending on what inputs and outputs the scaffold protein coordinates with PKA. For example, the AKAPs (A-kinase anchoring proteins), which link protein kinase A (PKA) to diverse signaling processes, all share a common short peptide motif that binds to the regulatory subunit of PKA ( 4). In some cases, homologous individual interaction motifs can be found in scaffolds associated with particular signaling proteins. Structure, Interactions and Mechanisms of Ste5: MAPK Pathway Scaffold Protein We review our current understanding of these organizational proteins: the types of pathways that they coordinate, the ways that they shape signaling responses, their biochemical and structural mechanisms, and how they are used in evolution or engineering to change signaling behaviors. These proteins have captured the attention of the signaling field because they appear to provide a simple and elegant solution for determining the specificity of information flow in intracellular networks ( 2, 11, 12). Over 15 years ago, the first scaffold proteins were discovered – proteins that coordinate the physical assembly of components of a signaling pathway or network ( 5– 10). ![]() Another solution is to assemble functionally interacting proteins into specific complexes. For example, functionally interacting signaling components can be sequestered into specific subcellular compartments (e.g. How can signaling proteins find their correct partners, and avoid their incorrect partners, among so many other proteins?Ī principle that has emerged over the last two decades is that cells achieve specificity in their molecular signaling networks by organizing discrete subsets of proteins in space and time ( Fig. Given this enormous number of molecules, it seems remarkable that cells can accurately process the vast array of signaling information they constantly receive. Mammalian cells contain an estimated one billion individual protein molecules, with as many as 10 percent of these involved in signal transduction ( 1).
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