Photo Regulation of Small G-Protein Ras using Photochromic Peptide

Abstract

The small guanine nucleotide binding protein (G-protein), which are known as a molecular switch is central regulator of cellular signaling pathway. The regulation mechanism of the protein is well studied at molecular level. Ras is one of the G-protein which have essential role in signaling cascade reaction in cell is regulated by guanine nucleotide exchange factor (GEF) and GTPase activating protein (GAP). GTP bout Ras induced by GEF is active state and GDP bound Ras induced by GAP is inactive state. The conformational change induced by GTP binding enable Ras to transduce a signal into downstream through direct interaction with its effectors. Also, mutant Ras known as constant active state cause excess signaling transduction to downstream effectors, which is pathogenesis of canceration, In this study, we focused on the interaction between Ras and its GEF, Son of sevenless (SOS) in order to control Ras function using photochromic compounds. Previously it is shown that the peptide mimicking the αH-helix, Ras binding region of SOS effectively inhibits Ras function competing with native SOS. Therefore, it is expected that photo-induced structural change of the peptide conjugate with photo-switch enable us to control Ras activity. We designed and synthesized SOS αH-helix peptide which contains two cysteine residues in order to cross-link with bi-functional photochromic molecule of azobenzene derivative, ABDM which change its structure reversibly by UV-VIS irradiation. The peptide modified with ABDM exhibited secondary structural change reversibly upon UV and visible light irradiation. Binding of ABDM-peptide to Ras and SOS dependent nucleotide exchange reaction were also altered photo-reversibly. We also tried to examine the photo-reversible effect of ABDM-peptide for HeLa cell.