Xanthopsins

B. Perman, V. Srajer, Z. Ren, T. Teng, C. Pradervand, T. Ursby, D. Bourgeois, F. Schotte, M. Wulff, R. Kort, K. HeUingwerf, and K. Moffat, Energy transduction on the nanosecond time scale early structural events in a xanthopsin photocycle. Science 279, 1946-1950 (1998). 

Xanthopsins. This family contains/j-coumaric acid chromophores. PYP belongs to this family (Figure 6.4). 

J. Hendriks, K.J. Hellingwerf, Photoactive Yellow Protein, the Prott pe Xanthopsin, Chapter 123 in [1]. 

Hendriks, J. and HeUingwerf, K.J. (2004) Photoactive Yellow Protein, the Prototype Xanthopsin, in CRC Handbook of Organic Photochemistry and Photobiology, 2nd edn (eds W.M. Horspool and F. Lend), CRC Press,... 

Discovery and Biological Context of the Photoactive Yellow Protein Xanthopsins The Family of Photoactive Yellow Proteins Photoactive Yellow Protein The Prototypical... 

As described above, PYP is part of a family of proteins named Xanthopsins, which thus far have only been identified in proteobacteria. Nevertheless, PYP also shows striking similarities to the much larger family of PAS domains. These PAS domains were identified in proteins from all three kingdoms of fife, i.e., in the Bacteria, the Archaea, and the Eucarya. PAS is an acronym formed from the names of the proteins in which the PAS motive was first recognized the Drosophila period clock protein (PER), the vertebrate aryl hydrocarbon receptor nuclear translocator (ARNT), and the Drosophila single-minded protein (SIM). 

In photoactive proteins, the chromophore is at the heart of its functional characteristics. The type of chromophore in a photoactive protein typically corresponds with the wavelength range in which the holoprotein needs to be active. In agreement with this, the Xanthopsins were shown to use an aromatic chromophore. This chromophore was identified in Halorhodospira halophila in 1994 as 4-hydroxycin-namic acid, covalently bound to the apoprotein via a thiol ester linkage with Cys69. ... 

These three major steps — isomerization, protonation change, and recovery — are also observed in the sensory rhodopsins, which have a similar cellular function as PYP but are structurally different. It is interesting to note that although the Xanthopsins and sensory rhodopsins evolved separately, the photochemical mechanism they use to generate a signal from an absorbed photon is essentially the same. 

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