Journal of the American Chemical Society
Journal of the American Chemical Society
5 years ago

Photoactivation of the BLUF Protein PixD Probed by the Site-Specific Incorporation of Fluorotyrosine Residues

Photoactivation of the BLUF Protein PixD Probed by the Site-Specific Incorporation of Fluorotyrosine Residues
Anil Verma, Agnieszka A. Gil, Grace E. Yoon, James N. Iuliano, Stephen R. Meech, Christopher R. Hall, Michael Towrie, Richard Brust, Andras Lukacs, Jarrod B. French, Gregory M. Greetham, Sergey P. Laptenok, Peter J. Tonge
The flavin chromophore in blue-light-using FAD (BLUF) photoreceptors is surrounded by a hydrogen bond network that senses and responds to changes in the electronic structure of the flavin on the ultrafast time scale. The hydrogen bond network includes a strictly conserved Tyr residue, and previously we explored the role of this residue, Y21, in the photoactivation mechanism of the BLUF protein AppABLUF by the introduction of fluorotyrosine (F-Tyr) analogues that modulated the pKa and reduction potential of Y21 by 3.5 pH units and 200 mV, respectively. Although little impact on the forward (dark- to light-adapted form) photoreaction was observed, the change in Y21 pKa led to a 4000-fold increase in the rate of dark-state recovery. In the present work we have extended these studies to the BLUF protein PixD, where, in contrast to AppABLUF, modulation in the Tyr (Y8) pKa has a profound impact on the forward photoreaction. In particular, a decrease in Y8 pKa by 2 or more pH units prevents formation of a stable light state, consistent with a photoactivation mechanism that involves proton transfer or proton-coupled electron transfer from Y8 to the electronically excited FAD. Conversely, the effect of pKa on the rate of dark recovery is markedly reduced in PixD. These observations highlight very significant differences between the photocycles of PixD and AppABLUF, despite their sharing highly conserved FAD binding architectures.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b07849

DOI: 10.1021/jacs.7b07849

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.