title: Direct observation of the pH-dependent equilibrium between L-like and M intermediates of photoactive yellow protein.
abstract: Equilibrium between the photoproducts of photoactive yellow protein (PYP), present in a millisecond time scale, was studied. The near-UV intermediate of PYP (PYPM) was red-shifted by alkalization due to the deprotonation of the chromophore (pKa=10.2). In addition, a small amount of red-shifted intermediate coexisted with PYPM. Its spectral shape in the visible region agreed with that of PYPL, the precursor of PYPM. The fraction of PYPL-like product was maximal at pH 10. It decays with a rate constant identical to that of PYPM. These results indicate that PYPL-like product is in pH-dependent equilibrium with PYPM and deprotonated PYPM.
authors.affiliation: Graduate School of Materials Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan. imamoto@ms.naist.jp
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Imamoto
authors.forename: Miki
authors.initials: M
authors.lastname: Harigai
authors.forename: Mikio
authors.initials: M
authors.lastname: Kataoka
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D020283:Photoreceptors, Microbial / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; D011994:Recombinant Proteins; C050162:photoactive yellow protein, Bacteria