Role of Phe1010 in Light-Induced Structural Changes of the neo1-LOV2 Domain of Adiantum
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- 作者：Atsushi Yamamoto ; Tatsuya Iwata ; Satoru Tokutomi ; Hideki Kandori
- 刊名：Biochemistry
- 出版年：2008
- 出版时间：January 22, 2008
- 年：2008
- 卷：47
- 期：3
- 页码：922 - 928
- 全文大小：433K
- 年卷期：v.47,no.3(January 22, 2008)
- ISSN：1520-4995
文摘
Phototropin (phot) is a blue-light sensor protein that elicits several photo responses in plants.Phototropin has two flavin mononucleotide (FMN)-binding domains, LOV1 and LOV2, in its N-terminalhalf. The C-terminal half is a blue-light-regulated Ser/Thr kinase. Various functional studies have reportedthat only LOV2 is responsible for the kinase activity, whereas the X-ray crystallographic structures of theLOV1 and LOV2 domains are almost identical. How does such a functional difference emerge? Ourprevious FTIR study of the LOV domains of Adiantum neochrome1 (neo1) showed that light-inducedprotein structural changes are small and temperature independent for neo1-LOV1, whereas the structuralchanges are large and highly temperature dependent for neo1-LOV2, which involve loops, 
-helices, and
-sheets. These observations successfully explained the different functions in terms of protein structuralchanges. They also suggested the presence of some crucial amino acids responsible for greater proteinstructural changes in the LOV2 domain. Here, we focused on phenylalanine-1010 (Phe1010) in neo1-LOV2, where FMN is sandwiched between Phe1010 and the reactive cysteine. Phenylalanine at this positionis conserved for LOV2 domains, while the corresponding amino acid is leucine for LOV1 domains inalmost all plant phototropins. We observed that unlike wild-type LOV2, the FTIR spectra of F1010LLOV2 exhibited no temperature dependence in the -helical and -sheet regions and that spectral changesin amide-I of these regions were significantly reduced, which was similar to LOV1. Thus, the replacementof phenylalanine with leucine converts neo1-LOV2 into neo1-LOV1 in terms of protein structural changesthat must be related to the different functions. We will discuss the roles of phenylalanine and leucine inthe LOV2 and LOV1 domains, respectively.
-helices, and-sheets. These observations successfully explained the different functions in terms of protein structuralchanges. They also suggested the presence of some crucial amino acids responsible for greater proteinstructural changes in the LOV2 domain. Here, we focused on phenylalanine-1010 (Phe1010) in neo1-LOV2, where FMN is sandwiched between Phe1010 and the reactive cysteine. Phenylalanine at this positionis conserved for LOV2 domains, while the corresponding amino acid is leucine for LOV1 domains inalmost all plant phototropins. We observed that unlike wild-type LOV2, the FTIR spectra of F1010LLOV2 exhibited no temperature dependence in the -helical and -sheet regions and that spectral changesin amide-I of these regions were significantly reduced, which was similar to LOV1. Thus, the replacementof phenylalanine with leucine converts neo1-LOV2 into neo1-LOV1 in terms of protein structural changesthat must be related to the different functions. We will discuss the roles of phenylalanine and leucine inthe LOV2 and LOV1 domains, respectively.