title: Influence of a chromophore analogue in the protein cage of a photoactive yellow protein.
abstract: Time-resolved spectra of a photoactive yellow protein (PYP) containing cyano-p-coumaric acid (CHCA) were recorded. To understand the mechanism of photo-isomerization, an electron-withdrawing CN group was introduced into the PYP to alter the C[double bond, length as m-dash]C double bond character. Free CHCA chromophores in aqueous solution underwent photo-isomerization whereas PYP with a bound CHCA (PYP-CN) exhibited no photocycle at acidic or alkaline pH or in urea and other solutions. Furthermore, no photocycle was observed with PYP mutants after illumination. This phenomenon cannot be fully explained by the electron-withdrawing properties of the CN group. We conclude that the CHCA chromophore in PYP was locked in the protein cage and that the CN group interacted with the protein residues.
authors.affiliation: Science & Technology Entrepreneurship Laboratory (e-square), Osaka University, 2-1 Yamadaoka, Suita, Osaka, Japan. hamada@uic.osaka-u.ac.jp.
authors.forename: Norio
authors.initials: N
authors.lastname: Hamada
authors.forename: Zhe
authors.initials: Z
authors.lastname: Tan
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kanematsu
authors.forename: Naoya
authors.initials: N
authors.lastname: Inazumi
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Nakamura
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D003373:Coumaric Acids / Q000737:chemistry; D004583:Electrons; D004926:Escherichia coli; D006863:Hydrogen-Ion Concentration; D008027:Light; D008164:Luminescent Proteins / Q000737:chemistry* / Q000235:genetics; D015394:Molecular Structure; D009154:Mutation; D011422:Propionates; D013057:Spectrum Analysis
chemical_list: D001426:Bacterial Proteins; D003373:Coumaric Acids; D008164:Luminescent Proteins; D011422:Propionates; C054562:yellow fluorescent protein, Bacteria; C495469:p-coumaric acid