1. Calmodulin extracts the Ras family protein RalA from lipid bilayers by engagement with two membrane-targeting motifs.
- Author
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Chamberlain SG, Gohlke A, Shafiq A, Squires IJ, Owen D, and Mott HR
- Subjects
- Amino Acid Motifs, Binding Sites, Calmodulin chemistry, Cell Membrane metabolism, Humans, Lipid Bilayers chemistry, Molecular Structure, Nuclear Magnetic Resonance, Biomolecular, Phosphorylation, Protein Binding, Protein Prenylation, Serine metabolism, ral GTP-Binding Proteins chemistry, Calmodulin metabolism, Lipid Bilayers metabolism, ral GTP-Binding Proteins metabolism
- Abstract
RalA is a small GTPase and a member of the Ras family. This molecular switch is activated downstream of Ras and is widely implicated in tumor formation and growth. Previous work has shown that the ubiquitous Ca
2+ -sensor calmodulin (CaM) binds to small GTPases such as RalA and K-Ras4B, but a lack of structural information has obscured the functional consequences of these interactions. Here, we have investigated the binding of CaM to RalA and found that CaM interacts exclusively with the C terminus of RalA, which is lipidated with a prenyl group in vivo to aid membrane attachment. Biophysical and structural analyses show that the two RalA membrane-targeting motifs (the prenyl anchor and the polybasic motif) are engaged by distinct lobes of CaM and that CaM binding leads to removal of RalA from its membrane environment. The structure of this complex, along with a biophysical investigation into membrane removal, provides a framework with which to understand how CaM regulates the function of RalA and sheds light on the interaction of CaM with other small GTPases, including K-Ras4B., Competing Interests: Competing interest statement: A.G. is an employee of AstraZeneca Ltd.- Published
- 2021
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