Complete chemical structure of photoactive yellow protein: novel thioester-linked 4-hydroxycinnamyl chromophore and photocycle chemistry.

摘要: The unique ability of photoactive proteins to capture and use energy from a photon light depends on the chromophore, its linkage protein, surrounding protein environment. To understand molecular mechanisms by which chromophore interact undergo cycle, we are studying yellow (PYP), 14-kDa water-soluble photoreceptor Ectothiorhodospira halophila with photocycle similar that sensory rhodopsin. Here, report cloning sequencing pyp gene chemical identification both covalent protein. Elemental composition data high-resolution mass spectrometry proteolytically derived chromopeptide, pH titrations UV-visible spectroscopy protein-bound chemically released fragmentation liberated amide were combined results 1.4-A-resolution crystal structure identify in PYP as 4-hydroxycinnamyl group covalently bound sole cysteine residue via thioester linkage. While 4-hydroxycinnamate is metabolic product phenylpropanoid pathway key molecule plant stress response, this first modification group. In dark (yellow) state PYP, stabilizes deprotonated phenolate anion. By combining our biochemical characterization other published observations, propose basis for photocycle: following initial absorption photon, involves protonation neutral phenol form corresponding observed photobleached intermediate.