Journal Article

Tryptophan at Position 104 is Involved in Transforming Light Signal into Changes of β-sheet Structure for the Signaling State in the BLUF Domain of AppA

Shinji Masuda, Koji Hasegawa and Taka-aki Ono

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 12, pages 1894-1901
Published in print December 2005 | ISSN: 0032-0781
Published online December 2005 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pci208
Tryptophan at Position 104 is Involved in Transforming Light Signal into Changes of β-sheet Structure for the Signaling State in the BLUF Domain of AppA

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AppA is a member of an FAD-based new class blue-light sensory protein known as sensor of blue light using FAD (BLUF) protein. The spectroscopic properties of an AppA BLUF domain (AppA126), in which the tryptophan residue at position 104 had been replaced with alanine (W104A), were characterized. The W104A mutant AppA126 showed a nearly normal absorption red shift in the FAD UV-visible absorption upon illumination; however, the light state relaxed to the dark state at a rate approximately 150 times faster than that of wild-type AppA126. Light-induced structural changes of FAD and apoprotein in the wild-type and mutant AppA126 were studied by means of light-induced Fourier transform infrared (FTIR) difference spectroscopy using AppA126, in which the apoprotein had been selectively labeled with 13C. The light-induced FTIR spectrum of the W104A mutant AppA126 revealed bands corresponding to a C4 = O stretch of the FAD isoalloxazine ring and structural changes of apoprotein, but with some alterations in the bands’ features. Notably, however, prominent protein bands at 1,632(+)/1,619(–) cm–1 caused by changes in the β-sheet structure were eliminated by the mutation, indicating that Trp104 is responsible for transforming the light signal into a specific β-sheet structure change in the apoprotein of the AppA BLUF domain in the signaling state.

Keywords: AppA; Blue light receptor; BLUF; Flavin; FTIR; Signaling transduction; BLUF, sensor of blue light using FAD; FTIR, Fourier transform infrared

Journal Article.  5263 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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