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									                           BLRB
    BLUF-domain containing protein in
        Rhodobacter sphaeroides




Key enzymes in bacterial blue light-mediated signal transduction
                                     BlrB
• BLUF- containing protein in purple bacteria Rhodobacter sphaeroides
• BlrB is a homodimer of 2 similar-folded chains yet assymmetrically arranged in 4o
structure
• Each subunit contain:
          •Typical BLUF domain (β-sheet interface and FAD-bound α-helices)
          • C-terminal extended α-helices
             BLUF Domain
FAD
binding
pocket



Hydrogen –
bonding
Network
                  Key residues of BlrB
• Tyr 9, Gln 51, Asn 33
     • in FAD binding pocket
     • H-bond to the ring of
     FAD
     • critical in structural
     integrity

• Arg 32
     • on surface of FAD
     binding pocket
     • flexible side chain

• Ile 127, Trp 92, Met 94
      • Ile127 is from C-terminal
      extension
      • Significant chemical shift
      changes
      • Trp92 – highly conserved
       signaling switch point
         Proposed mechanism of action
• Light-induced changes in hydrogen bonding of C4=O trigger further
rearrangements of the hydrogen bonding network  conformational change within FAD
binding pocket
• Flexibility of Arg 32, not heavily involve in protein structural integrity 

• Light excitation
stimulates changes in
the hydrogen bonding
network involving O2
and
Arg-32,
• conformational
changes in the flavin
mediated through Arg-32
to the surface of the
Protein
 exposed amino acid
side chains trigger the
interaction with effector
modules
                             References
1. Wu, Q., Ko, W. H. & Gardner, K. H. (2008) Biochemistry 47, 10271-10280.
2. Jung, A., Domratcheva, T., Tarutina, M., Wu, Q., Ko, W. H., Shoeman, R. L.,
    Gomelsky, M., Gardner, K. H., and Schlichting, I. (2005) Proc. Natl. Acad.
    Sci.U.S.A. 102, 12350–12355.
3. Gauden, M., van Stokkum, I. H., Key, J. M., Luhrs, D., van Grondelle, R.,
    Hegemann, P., and Kennis, J. T. (2006) Proc. Natl. Acad. Sci. U.S.A. 103,
    10895–10900.
4. Takahashi, R., Okajima, K., Suzuki, H., Nakamura, H., Ikeuchi, M., and Noguchi,
    T. (2007) Biochemistry 46, 6459–6467.
5. Aravind, L. & Koonin, E. V. (1999) J. Mol. Biol. 287, 1023–1040.
6. Kita, A., Okajima, K., Morimoto, Y., Ikeuchi, M.&Miki, K. (2005) J. Mol. Biol. 349,
    1–9.
7. Anderson, S., Dragnea, V., Masuda, S., Ybe, J., Moffat, K. & Bauer, C. (2005)
    Biochemistry 44, 7998–8005.
8. Zirak, P., Penzkofer, A., Schiereis, T., Hegemann, P., Jung, A. & Schlichting, I.
    (2005) Chem. Phys. 315, 142–154.
9. Fedorov, R., Schlichting, I., Hartmann, E., Domratcheva, T., Fuhrmann, M. &
    Hegemann, P. (2003) Biophys. J. 84, 2474–2482.
10. Gauden, M., Grinstead, J. S., Laan, W., van Stokkum, I. H., Avila- Perez, M., Toh,
    K. C., Boelens, R., Kaptein, R., van Grondelle, R., Hellingwerf, K. J., and Kennis,
    J. T. (2007) Biochemistry 46, 7405–7415.
11. Masuda, S., Hasegawa, K., Ishii, A. & Ono, T. A. (2004) Biochemistry 43, 5304–
    5313.

								
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