Search results for "photoactivation"
showing 6 items of 6 documents
The three-dimensional structure of Drosophila melanogaster (6–4) photolyase at room temperature
2021
A crystal structure of a photolyase at room temperature confirms the structural information obtained from cryogenic crystallography and paves the way for time-resolved studies of the photolyase at an X-ray free-electron laser.
Structural photoactivation of a full-length bacterial phytochrome
2016
Time-resolved x-ray solution scattering reveals the conformational signaling mechanism of a bacterial phytochrome.
Tips and turns of bacteriophytochrome photoactivation
2020
Phytochromes are ubiquitous photosensor proteins, which control the growth, reproduction and movement in plants, fungi and bacteria. Phytochromes switch between two photophysical states depending on the light conditions. In analogy to molecular machines, light absorption induces a series of structural changes that are transduced from the bilin chromophore, through the protein, and to the output domains. Recent progress towards understanding this structural mechanism of signal transduction has been manifold. We describe this progress with a focus on bacteriophytochromes. We describe the mechanism along three structural tiers, which are the chromophore-binding pocket, the photosensory module,…
Sequential conformational transitions and α-helical supercoiling regulate a sensor histidine kinase
2017
Sensor histidine kinases are central to sensing in bacteria and in plants. They usually contain sensor, linker, and kinase modules and the structure of many of these components is known. However, it is unclear how the kinase module is structurally regulated. Here, we use nano- to millisecond time-resolved X-ray scattering to visualize the solution structural changes that occur when the light-sensitive model histidine kinase YF1 is activated by blue light. We find that the coiled coil linker and the attached histidine kinase domains undergo a left handed rotation within microseconds. In a much slower second step, the kinase domains rearrange internally. This structural mechanism presents a t…
DNA-binding and in vitro cytotoxic activity of platinum(II) complexes of curcumin and caffeine
2019
Abstract Three Pt(II) complexes containing the natural ligands curcumin and caffeine, namely [Pt(curc)(PPh3)2]Cl (1), [PtCl(curc)(DMSO)] (2) (curc = deprotonated curcumin) and trans-[Pt(caffeine)Cl2(DMSO)] (3), were synthesized and fully characterized. The data obtained suggest that, for both 1 and 2, the anion of curcumin is coordinated to the platinum ion via the oxygen atoms of the β-diketonate moiety. Spectroscopic features reveal that in 2 and 3, a DMSO molecule is S-bonded to the metal centre. For 3, all data indicate a square-planar geometry formed by a 9-N bonded caffeine, two trans chloride anions and a DMSO. The three complexes undergo changes in solution upon incubation for 24 h;…
Photoactive Yellow Protein Chromophore Photoisomerizes around a Single Bond if the Double Bond Is Locked
2020
Photoactivation in the Photoactive Yellow Protein, a bacterial blue light photoreceptor, proceeds via photo-isomerization of the double C=C bond in the covalently attached chromophore. Quantum chemistry calculations, however, have suggested that in addition to double bond photo-isomerization, the isolated chromophore and many of its analogues, can isomerize around a single C-C bond as well. Whereas double bond photo-isomerization has been observed with x-ray crystallography, experimental evidence for single bond photo-isomerization is currently lacking. Therefore, we have synthesized a chromophore analogue, in which the formal double bond is covalently locked in a cyclopentenone ring and ca…