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Light-induced structural changes of the LOV2 domains in various phototropins revealed by FTIR spectroscopy

View Article: PubMed Central - PubMed

ABSTRACT

Phototropin (Phot), a blue-light photoreceptor in plants, consists of two FMN-binding domains (named LOV1 and LOV2) and a serine/threonine (Ser/Thr) kinase domain. We have investigated light-induced structural changes of LOV domains, which lead to the activation of the kinase domain, by means of light-induced difference FTIR spectroscopy. FTIR spectroscopy revealed that the reactive cysteine is protonated in both unphotolyzed and triplet-excited states, which is difficult to detect by other methods such as X-ray crystallography. In this review, we describe the light-induced structural changes of hydrogen-bonding environment of FMN chromophore and protein backbone in Adiantum neo1-LOV2 in the C=O stretching region by use of 13C-labeled samples. We also describe the comprehensive FTIR analysis of LOV2 domains among Arabidopsis phot1, phot2, and Adiantum neo1 with and without Jα helix domain.

No MeSH data available.


Light-induced difference FTIR spectra for the LOV2 domain of Arabidopsis phot1(a), Arabidopsis phot2 (b), and Adiantum neo1 (c) in the 1750–1600 cm−1 region. LOV2-core (dotted lines) and LOV2-Jα (solid lines) are shown. The spectra were recorded at 150, 250, 260, 273, and 295K. This figure is modified from Ref 52 and 53.
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f5-7_89: Light-induced difference FTIR spectra for the LOV2 domain of Arabidopsis phot1(a), Arabidopsis phot2 (b), and Adiantum neo1 (c) in the 1750–1600 cm−1 region. LOV2-core (dotted lines) and LOV2-Jα (solid lines) are shown. The spectra were recorded at 150, 250, 260, 273, and 295K. This figure is modified from Ref 52 and 53.

Mentions: Figure 5 shows light-induced difference FTIR spectra of LOV2-core (dotted lines) and LOV2-Jα (solid lines) for Arabidopsis phot1 (a), Arabidopsis phot2 (b), and Adiantum neo1 (c) in the 1750–1600 cm−1 region. The light-induced difference spectra were measured in a wide temperature range (150–295 K). In addition to the amide-I vibrations, the C2=O and C4=O stretching vibrations of FMN also appear in this frequency region. Our study of neo1-LOV2 identified the frequencies at 1677 and 1711 cm−1 as the C2=O and C4=O stretching vibrations by use of 13C2=O- and 13C4=O-labeled FMN (Fig. 3). Similarly, negative bands at 1676 and 1712 cm−1 in Figure 5a and at 1678 and 1713 cm−1 in Figure 5b presumably originate from these vibrations in the unphotolyzed states of phot1 and phot2. It is likely that a higher frequency shift of both C2=O and C4=O stretches occurs in Figure 5, implying common structural changes of FMN among phot1, phot2, and neo1. Similar changes between LOV2-core and LOV2-Jα also indicate that the presence of the Jα helix does not affect structural perturbation of FMN.


Light-induced structural changes of the LOV2 domains in various phototropins revealed by FTIR spectroscopy
Light-induced difference FTIR spectra for the LOV2 domain of Arabidopsis phot1(a), Arabidopsis phot2 (b), and Adiantum neo1 (c) in the 1750–1600 cm−1 region. LOV2-core (dotted lines) and LOV2-Jα (solid lines) are shown. The spectra were recorded at 150, 250, 260, 273, and 295K. This figure is modified from Ref 52 and 53.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC5036776&req=5

f5-7_89: Light-induced difference FTIR spectra for the LOV2 domain of Arabidopsis phot1(a), Arabidopsis phot2 (b), and Adiantum neo1 (c) in the 1750–1600 cm−1 region. LOV2-core (dotted lines) and LOV2-Jα (solid lines) are shown. The spectra were recorded at 150, 250, 260, 273, and 295K. This figure is modified from Ref 52 and 53.
Mentions: Figure 5 shows light-induced difference FTIR spectra of LOV2-core (dotted lines) and LOV2-Jα (solid lines) for Arabidopsis phot1 (a), Arabidopsis phot2 (b), and Adiantum neo1 (c) in the 1750–1600 cm−1 region. The light-induced difference spectra were measured in a wide temperature range (150–295 K). In addition to the amide-I vibrations, the C2=O and C4=O stretching vibrations of FMN also appear in this frequency region. Our study of neo1-LOV2 identified the frequencies at 1677 and 1711 cm−1 as the C2=O and C4=O stretching vibrations by use of 13C2=O- and 13C4=O-labeled FMN (Fig. 3). Similarly, negative bands at 1676 and 1712 cm−1 in Figure 5a and at 1678 and 1713 cm−1 in Figure 5b presumably originate from these vibrations in the unphotolyzed states of phot1 and phot2. It is likely that a higher frequency shift of both C2=O and C4=O stretches occurs in Figure 5, implying common structural changes of FMN among phot1, phot2, and neo1. Similar changes between LOV2-core and LOV2-Jα also indicate that the presence of the Jα helix does not affect structural perturbation of FMN.

View Article: PubMed Central - PubMed

ABSTRACT

Phototropin (Phot), a blue-light photoreceptor in plants, consists of two FMN-binding domains (named LOV1 and LOV2) and a serine/threonine (Ser/Thr) kinase domain. We have investigated light-induced structural changes of LOV domains, which lead to the activation of the kinase domain, by means of light-induced difference FTIR spectroscopy. FTIR spectroscopy revealed that the reactive cysteine is protonated in both unphotolyzed and triplet-excited states, which is difficult to detect by other methods such as X-ray crystallography. In this review, we describe the light-induced structural changes of hydrogen-bonding environment of FMN chromophore and protein backbone in Adiantum neo1-LOV2 in the C=O stretching region by use of 13C-labeled samples. We also describe the comprehensive FTIR analysis of LOV2 domains among Arabidopsis phot1, phot2, and Adiantum neo1 with and without Jα helix domain.

No MeSH data available.