Structural requirements for key residues and auxiliary portions of a BLUF domain

Qiong Wu, Wen Huang Ko, Kevin H. Gardner

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

BlrB in Rhodobacter sphaeroides is a single domain, flavin-based blue light sensor protein in the BLUF family of photoreceptors. Consistent with other members of this family, blue light excitation induces a putative signaling state characterized by a 10 nm red shift in the UV-visible absorbance spectrum. Structural and spectroscopic characterization of truncated BlrB constructs establishes that the C-terminal 50 amino acids of this protein are essential to its structural integrity despite not being part of the canonical BLUF domain architecture. Mutagenesis studies support the critical roles of Tyr9, Asn33, and Gln51 for flavin binding and the integrity of the BLUF domain fold. Comparison of solution NMR spectra of BlrB acquired under dark and light conditions indicates very limited light-dependent conformational changes except for a few interesting residues: Trp92, Met94, and Ile127. Notably, the Ile127 side chain experiences significant chemical shift changes despite the fact that it is far (∼15 Å) from the flavin chromophore in the C-terminal extension. These data suggest that the light-induced signal is propagated from the flavin through the β sheet to the last two α helices in the C-terminal extension, potentially providing a mechanism to transmit this change to initiate a cellular response to blue light.

Original languageEnglish (US)
Pages (from-to)10271-10280
Number of pages10
JournalBiochemistry
Volume47
Issue number39
DOIs
StatePublished - Sep 30 2008

ASJC Scopus subject areas

  • Biochemistry

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