Allosteric transition induced by Mg²⁺ ion in a transactivator monitored by SERS

Abstract

We demonstrate the utility of the Surface-enhanced Raman Spectroscopy (SERS) to monitor conformational transitions in protein upon ligand binding. The changes in protein’s secondary and tertiary structures were monitored using amide and aliphatic/aromatic side chain vibrations. Changes in these bands are suggestive of the stabilization of the secondary and tertiary structure of transcription activator protein C in the presence of Mg²⁺ ion, whereas the spectral fingerprint remained unaltered in the case of a mutant protein, defective in Mg²⁺ binding. The importance of the acidic residues in Mg²⁺ binding, which triggers an overall allosteric transition in the protein, is visualized in the molecular model. The present study thus opens up avenues toward the application of SERS as a potential tool for gaining structural insights into the changes occurring during conformational transitions in proteins.