文章基本信息

标题：Evidence for Tautomerisation of Glutamine in BLUF Blue Light Receptors by Vibrational Spectroscopy and Computational Chemistry
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作者：Tatiana Domratcheva ; Elisabeth Hartmann ; Ilme Schlichting 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2016
卷号：6
期号：1
DOI：10.1038/srep22669
语种：English
出版社：Springer Nature
摘要：BLUF (blue light sensor using flavin) domains regulate the activity of various enzymatic effector domains in bacteria and euglenids. BLUF features a unique photoactivation through restructuring of the hydrogen-bonding network as opposed to a redox reaction or an isomerization of the chromophore. A conserved glutamine residue close to the flavin chromophore plays a central role in the light response, but the underlying modification is still unclear. We labelled this glutamine with (15)N in two representative BLUF domains and performed time-resolved infrared double difference spectroscopy. The assignment of the signals was conducted by extensive quantum chemical calculations on large models with 187 atoms reproducing the UV-vis and infrared signatures of BLUF photoactivation. In the dark state, the comparatively low frequency of 1,667 cm(-1) is assigned to the glutamine C=O accepting a hydrogen bond from tyrosine. In the light state, the signature of a tautomerised glutamine was extracted with the C=N stretch at ~1,691 cm(-1) exhibiting the characteristic strong downshift by (15)N labelling. Moreover, an indirect isotope effect on the flavin C4=O stretch was found. We conclude that photoactivation of the BLUF receptor does not only involve a rearrangement of hydrogen bonds but includes a change in covalent bonds of the protein.