Limits...
FTIR Spectroscopy Revealing Light-Dependent Refolding of the Conserved Tongue Region of Bacteriophytochrome.

Stojković EA, Toh KC, Alexandre MT, Baclayon M, Moffat K, Kennis JT - J Phys Chem Lett (2014)

Bottom Line: Our results indicate conversion from a β-sheet to an α-helical element in the so-called tongue region of the PHY domain, consistent with recent X-ray structures of Deinococcus radiodurans DrBphP in dark and light states (Takala H.; et al.Nature2014, 5, 245-248).A conserved Asp in the GAF domain that noncovalently connects with the PHY domain and a conserved Pro in the tongue region of the PHY domain are essential for the β-sheet-to-α-helix conversion.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology and Institute for Biophysical Dynamics, The University of Chicago , Chicago, Illinois 60637, United States.

ABSTRACT
Bacteriophytochromes (BphPs) constitute a class of photosensory proteins that toggle between Pr and Pfr functional states through absorption of red and far-red light. The photosensory core of BphPs is composed of PAS, GAF, and PHY domains. Here, we apply FTIR spectroscopy to investigate changes in the secondary structure of Rhodopseudomonas palustris BphP2 (RpBphP2) upon Pr to Pfr photoconversion. Our results indicate conversion from a β-sheet to an α-helical element in the so-called tongue region of the PHY domain, consistent with recent X-ray structures of Deinococcus radiodurans DrBphP in dark and light states (Takala H.; et al. Nature2014, 5, 245-248). A conserved Asp in the GAF domain that noncovalently connects with the PHY domain and a conserved Pro in the tongue region of the PHY domain are essential for the β-sheet-to-α-helix conversion.

No MeSH data available.


DrBphP X-ray structures of BV (cyan)–GAF (green) and tonguein the PHY domain (pink) in Pr (A) and Pfr (B)1 (PDB IDcodes 4O0P and 4O01, respectively);partial sequence alignment of previously characterized BphPs and Synechocystis sp. Cph1, highlighting the conservedPRXSF motif of the PHY domain (C).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4126705&req=5

fig1: DrBphP X-ray structures of BV (cyan)–GAF (green) and tonguein the PHY domain (pink) in Pr (A) and Pfr (B)1 (PDB IDcodes 4O0P and 4O01, respectively);partial sequence alignment of previously characterized BphPs and Synechocystis sp. Cph1, highlighting the conservedPRXSF motif of the PHY domain (C).

Mentions: The determinationof crystal structures of various BphPs and thecyanobacterial phytochrome Cph1 has explored the light-activated functionof phytochromes.5,6,9−12 BphPs bind BV through a covalent thioether linkage to the PAS domain.BV is largely embedded in the GAF domain, which provides most of thehydrogen-bonding, steric, and hydrophobic interactions that securethe chromophore in position.5,9,11,13 The pyrrole rings form an intricatehydrogen-bond network with a conserved Asp of the PASDIP motif inthe GAF domain (Figure 1). In addition, a conservedHis in the GAF domain and a water molecule were shown to interactwith the pyrrole nitrogens in the previously published structures9,10 (the His was omitted in Figure 1 for clarity,while the pyrrole water was not resolved in the DrBphP structures).The PHY domain forms an extension to the chromophore-binding domainof phytochromes that works in tandem with the GAF domain to tune spectralproperties and facilitate physiologically functional photochemistry.Crystal structures of the complete photosensory core module comprisingthe PAS-GAF-PHY domains are available for Synechocystissp. Cph1 in the Pr state14 and Pseudomonas aeruginosa PaBphPin the Pfr state.5 The latter is a so-called“bathy” phytochrome that assembles as Pr but rapidlythermally converts to its stable Pfr15 form.Deletion of the PHY domain affects the photochemistry and impairsPfr formation11,16 in all referenced BphPs. ThePHY domain engages the chromophore pocket through a salt bridge betweenthis conserved Asp and a conserved Arg and seals off the chromophorefrom contact with the solvent through a conserved secondary structureelement known as the “tongue” (Figure 1).


FTIR Spectroscopy Revealing Light-Dependent Refolding of the Conserved Tongue Region of Bacteriophytochrome.

Stojković EA, Toh KC, Alexandre MT, Baclayon M, Moffat K, Kennis JT - J Phys Chem Lett (2014)

DrBphP X-ray structures of BV (cyan)–GAF (green) and tonguein the PHY domain (pink) in Pr (A) and Pfr (B)1 (PDB IDcodes 4O0P and 4O01, respectively);partial sequence alignment of previously characterized BphPs and Synechocystis sp. Cph1, highlighting the conservedPRXSF motif of the PHY domain (C).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126705&req=5

fig1: DrBphP X-ray structures of BV (cyan)–GAF (green) and tonguein the PHY domain (pink) in Pr (A) and Pfr (B)1 (PDB IDcodes 4O0P and 4O01, respectively);partial sequence alignment of previously characterized BphPs and Synechocystis sp. Cph1, highlighting the conservedPRXSF motif of the PHY domain (C).
Mentions: The determinationof crystal structures of various BphPs and thecyanobacterial phytochrome Cph1 has explored the light-activated functionof phytochromes.5,6,9−12 BphPs bind BV through a covalent thioether linkage to the PAS domain.BV is largely embedded in the GAF domain, which provides most of thehydrogen-bonding, steric, and hydrophobic interactions that securethe chromophore in position.5,9,11,13 The pyrrole rings form an intricatehydrogen-bond network with a conserved Asp of the PASDIP motif inthe GAF domain (Figure 1). In addition, a conservedHis in the GAF domain and a water molecule were shown to interactwith the pyrrole nitrogens in the previously published structures9,10 (the His was omitted in Figure 1 for clarity,while the pyrrole water was not resolved in the DrBphP structures).The PHY domain forms an extension to the chromophore-binding domainof phytochromes that works in tandem with the GAF domain to tune spectralproperties and facilitate physiologically functional photochemistry.Crystal structures of the complete photosensory core module comprisingthe PAS-GAF-PHY domains are available for Synechocystissp. Cph1 in the Pr state14 and Pseudomonas aeruginosa PaBphPin the Pfr state.5 The latter is a so-called“bathy” phytochrome that assembles as Pr but rapidlythermally converts to its stable Pfr15 form.Deletion of the PHY domain affects the photochemistry and impairsPfr formation11,16 in all referenced BphPs. ThePHY domain engages the chromophore pocket through a salt bridge betweenthis conserved Asp and a conserved Arg and seals off the chromophorefrom contact with the solvent through a conserved secondary structureelement known as the “tongue” (Figure 1).

Bottom Line: Our results indicate conversion from a β-sheet to an α-helical element in the so-called tongue region of the PHY domain, consistent with recent X-ray structures of Deinococcus radiodurans DrBphP in dark and light states (Takala H.; et al.Nature2014, 5, 245-248).A conserved Asp in the GAF domain that noncovalently connects with the PHY domain and a conserved Pro in the tongue region of the PHY domain are essential for the β-sheet-to-α-helix conversion.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology and Institute for Biophysical Dynamics, The University of Chicago , Chicago, Illinois 60637, United States.

ABSTRACT
Bacteriophytochromes (BphPs) constitute a class of photosensory proteins that toggle between Pr and Pfr functional states through absorption of red and far-red light. The photosensory core of BphPs is composed of PAS, GAF, and PHY domains. Here, we apply FTIR spectroscopy to investigate changes in the secondary structure of Rhodopseudomonas palustris BphP2 (RpBphP2) upon Pr to Pfr photoconversion. Our results indicate conversion from a β-sheet to an α-helical element in the so-called tongue region of the PHY domain, consistent with recent X-ray structures of Deinococcus radiodurans DrBphP in dark and light states (Takala H.; et al. Nature2014, 5, 245-248). A conserved Asp in the GAF domain that noncovalently connects with the PHY domain and a conserved Pro in the tongue region of the PHY domain are essential for the β-sheet-to-α-helix conversion.

No MeSH data available.