Ultrafast Structural Dynamics in BLUF Domains: Transient Infrared Spectroscopy of AppA and Its Mutants

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• 作者：Allison L. Stelling ; Kate L. Ronayne ; Jé ; rô ; me Nappa ; Peter J. Tonge ; Stephen R. Meech
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：December 19, 2007
• 年：2007
• 卷：129
• 期：50
• 页码：15556 - 15564
• 全文大小：287K
• 年卷期：v.129,no.50(December 19, 2007)
• ISSN：1520-5126

文摘

The structural dynamics following photoexcitation of a photosensing BLUF (blue light sensingusing FAD) domain protein have been investigated by ultrafast transient infrared spectroscopy. Specifically,the transcriptional antirepressor AppA from Rhodobacter sphaeroides has been studied in the light anddark adapted forms and in photoactive and inactive mutants W104F and Q63L. A transient absorption hasbeen observed at 1666 cm^-1 which is a marker mode for the photoactive state of the protein. Thisinstantaneously formed transient is tentatively assigned to a vibrational mode of a protein residue modifiedthrough its interaction with the excited state of the chromophore. A plausible candidate consistent with themutant studies is the carbonyl stretch of the Q63 amide side chain. These results suggest that modificationof the strength of protein chromophore H-bonded interactions is the primary step in the BLUF domainphotocycle. No new species were observed to be formed during the first nanosecond. Measurement of theultrafast ground state recovery showed that the excited state of light adapted AppA is strongly quenchedcompared to the dark adapted state. It is proposed that the reorganization which occurs to form the signalingstate is favorable to electron-transfer quenching.