Light-Induced Conformational Change and Transient Dissociation Reaction of the BLUF Photoreceptor Synechocystis PixD (Slr1694)

JOURNAL OF MOLECULAR BIOLOGY

卷:409

Article

Tanaka, Keisuke¹  Nakasone, Yusuke¹  Okajima, Koji^2,3  Ikeuchi, Masahiko²  Tokutomi, Satoru³  Terazima, Masahide¹ 

[1] Kyoto Univ, Grad Sch Sci, Dept Chem, Kyoto 6068502, Japan

[2] Univ Tokyo, Grad Sch Arts & Sci, Dept Life Sci Biol, Meguro Ku, Tokyo 1538902, Japan

[3] Osaka Prefecture Univ, Grad Sch Sci, Dept Biol Sci, Osaka 5998531, Japan

关键词: photoreceptor;    BLUF;    dynamics;    diffusion;    transient grating;   

DOI  :  10.1016/j.jmb.2011.04.032

来源: Elsevier

【 摘 要 】

The light-induced reaction of the BLUF (blue light photoreceptor using flavin adenine dinucleotide) photoreceptor PixD from Synechocystis sp. PCC6803 (Slr1694) was investigated using the time-resolved transient grating method. A conformational change coupled with a volume contraction of 13 mL mol(-1) was observed with a time constant of 45 ms following photoexcitation. At a weak excitation light intensity, there were no further changes in volume and diffusion coefficient (D). The determined D-value (3.7 x 10(-11) m(2) s(-1)) suggests that PixD exists as a decamer in solution, and this oligomeric state was confirmed by size-exclusion chromatography and blue native polyacrylamide gel electrophoresis. Surprisingly, by increasing the excitation laser power, we observed a large increase in D with a time constant of 350 ms following the volume contraction reaction. The D-value of this photoproduct species (7.5 x 10(-11) m(2) s(-1)) is close to that of the PixD dimer. Combined with transient grating and size-exclusion chromatography measurements under light-illuminated conditions, the light-induced increase in D was attributed to a transient dissociation reaction of the PixD decamer to a dimer. For the M93A-mutated PixD, no volume or D-change was observed. Furthermore, we showed that the M93A mutant did not form the decamer but only the dimer in the dark state. These results indicate that the formation of the decamer and the conformational change around the Met residue are important factors that control the regulation of the downstream signal transduction by the PixD photoreceptor. (C) 2011 Elsevier Ltd. All rights reserved.

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