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Photodynamics of the small BLUF protein BlrB from Rhodobacter sphaeroides

Paper ID Volume ID Publish Year Pages File Format Full-Text
30818 44506 2006 15 PDF Available
Title
Photodynamics of the small BLUF protein BlrB from Rhodobacter sphaeroides
Abstract

The BLUF protein BlrB from the non-sulphur anoxyphototrophic purple bacterium Rhodobacter sphaeroides is characterized by absorption and emission spectroscopy. BlrB expressed from E. coli binding FAD, FMN, and riboflavin (called BrlBI) and recombinant BlrB containing only FAD (called BlrBII) are investigated. The dark-adapted proteins exist in two different receptor conformations (receptor states) with different sub-nanosecond fluorescence lifetimes (BLUFr,f and BLUFr,sl). Some of the flavin-cofactor (ca. 8%) is unbound in thermodynamic equilibrium with the bound cofactor. The two receptor conformations are transformed to putative signalling states (BLUFs,f and BLUFs,sl) of decreased fluorescence efficiency and shortened fluorescence lifetime by blue-light excitation. In the dark at room temperature both signalling states recover back to the initial receptor states with a time constant of about 2 s. Quantum yields of signalling state formation of about 90% for BlrBII and about 40% for BlrBI were determined by intensity dependent transmission measurements. Extended blue-light excitation causes unbound flavin degradation (formation of lumichrome and lumiflavin-derivatives) and bound cofactor conversion to the semiquinone form. The flavin-semiquinone further reduces and the reduced flavin re-oxidizes back in the dark. A photo-dynamics scheme is presented and relevant quantum efficiencies and time constants are determined.

Keywords
BLUF domain; BlrB from Rhodobacter sphaeroides; Blue-light photoreceptor; Absorption spectroscopy; Fluorescence spectroscopy; Photo-cycle; Photo-degradation; Photo-reduction; Flavoprotein; Flavins; FAD; Flavin-semiquinone
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Photodynamics of the small BLUF protein BlrB from Rhodobacter sphaeroides
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 83, Issue 3, 1 June 2006, Pages 180–194
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us