Photo-Control of RAS GDP-GTP Exchange using the SOSαH Mimicking Peptides Modified with Spiropyran Derivative

Abstract

Ras is a kind of GTPase protein, and it regulates cellular signal transduction. For example, some information such as cell growth and cell differentiation from in vitro to in vivo of downstream by cycling between GTP active form and GDP inactive form. GDP-GTP exchange of Ras is induced by binding of GEF(Guanine Exchange Factor) to Ras. Recently some kinds of peptide which interfere binding of GEF resulting in inhibition of GDP-GTP exchange, were reported. Synthetic peptide mimicking αH helix of SOS inhibited the Ras GDP-GTP exchange in the presence of SOS (Son Of Sevenless). Photochromic molecule, spiropyran isomerize between ring-closed spiro (SP) and ring-opened merocyanine (MC) forms photo-reversibly upon visible and ultraviolet lights. It is known that the zwitterion of MC forms exhibit dimerization. Previously, it has been demonstrated that the peptides modified with spiropyran derivatives change their secondary structure accompanied by formation of spiropyran dimerization photoreversibly. In this study, we designed and synthesized the peptides which have two cysteines and analogous to the SOS αH-helix. The two cysteine residues of the peptides were modified with SP-maleimide(SP-MA) stoichiometrically. The spiropyran incorporated into the peptide exhibited SP-MC isomerization upon visible light and ultraviolet light irradiations. The secondary structural change of the SOS mimic peptide induce by photo-isomerization of SP-MA were examined. Furthermore, photoreversible inhibition of Ras GDP-GTP exchange in the presence of SOS with the photochromic peptide was analyzed using fluorescent GDP analogues.