1. Ras activation by SOS: Allosteric regulation by altered fluctuation dynamics
- Author
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Iversen, Lars, Tu, Hsiung-Lin, Lin, Wan-Chen, Christensen, Sune M, Abel, Steven M, Iwig, Jeff, Wu, Hung-Jen, Gureasko, Jodi, Rhodes, Christopher, Petit, Rebecca S, Hansen, Scott D, Thill, Peter, Yu, Cheng-Han, Stamou, Dimitrios, Chakraborty, Arup K, Kuriyan, John, and Groves, Jay T
- Subjects
Underpinning research ,1.1 Normal biological development and functioning ,Allosteric Regulation ,Catalytic Domain ,Crystallography ,X-Ray ,Enzyme Activation ,Humans ,Kinetics ,Nucleotides ,Protein Interaction Domains and Motifs ,Proto-Oncogene Proteins p21(ras) ,Son of Sevenless Protein ,Drosophila ,General Science & Technology - Abstract
Activation of the small guanosine triphosphatase H-Ras by the exchange factor Son of Sevenless (SOS) is an important hub for signal transduction. Multiple layers of regulation, through protein and membrane interactions, govern activity of SOS. We characterized the specific activity of individual SOS molecules catalyzing nucleotide exchange in H-Ras. Single-molecule kinetic traces revealed that SOS samples a broad distribution of turnover rates through stochastic fluctuations between distinct, long-lived (more than 100 seconds), functional states. The expected allosteric activation of SOS by Ras-guanosine triphosphate (GTP) was conspicuously absent in the mean rate. However, fluctuations into highly active states were modulated by Ras-GTP. This reveals a mechanism in which functional output may be determined by the dynamical spectrum of rates sampled by a small number of enzymes, rather than the ensemble average.
- Published
- 2014