PixE promotes dark oligomerization of the BLUF photoreceptor PixD

Yuan, Hua; Bauer, Carl E.

doi:10.1073/pnas.0802149105

Cited by 63 publications

(99 citation statements)

References 24 publications

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“…S9). Because PixD is known to form a complex with the response regulator, PixE, and the complex is disassembled by the illumination of blue light in vivo (17,29,30), it is conceivable that the 1-min delay observed in Fig. 5 originates from the above reaction, whereas the role of PixE to the suppression is not yet clear.…”

Section: Discussionmentioning

confidence: 96%

Asymmetric distribution of type IV pili triggered by directional light in unicellular cyanobacteria

Nakane

Nishizaka

2017

Proc. Natl. Acad. Sci. U.S.A.

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The type IV pili (T4P) system is a supermolecular machine observed in prokaryotes. Cells repeat the cycle of T4P extension, surface attachment, and retraction to drive twitching motility. Although the properties of T4P as a motor have been scrutinized with biophysics techniques, the mechanism of regulation remains unclear. Here we provided the framework of the T4P dynamics at the single-cell level in Synechocystis sp. PCC6803, which can recognize light direction. We demonstrated that the dynamics was detected by fluorescent beads under an optical microscope and controlled by blue light that induces negative phototaxis; extension and retraction of T4P was activated at the forward side of lateral illumination to move away from the light source. Additionally, we directly visualized each pilus by fluorescent labeling, allowing us to quantify their asymmetric distribution. Finally, quantitative analyses of cell tracking indicated that T4P was generated uniformly within 0.2 min after blue-light exposure, and within the next 1 min the activation became asymmetric along the light axis to achieve directional cell motility; this process was mediated by the photo-sensing protein, PixD. This sequential process provides clues toward a general regulation mechanism of T4P system, which might be essentially common between archaella and other secretion apparatuses.Synechocystis sp. PCC6803 | twitching motility | phototaxis | signal transduction | fluorescence T ype IV pili (T4P) are fascinating supermolecular machines that drive twitching motility, protein secretion, and DNA uptake in prokaryotes (1). Twitching motility is now widely accepted as a form of bacterial translocation involving repetition of the cycle of extension and retraction of the pili (2, 3) (Fig. 1A), which is powered by assembly and disassembly ATPase at the base of helical pilus fibers (4). The mechanical response of a single pilus has been scrutinized in great detail using biophysical approaches such as optical tweezers methodology in Neisseria gonorrheae (3, 5-7), although the dynamic properties resulting from the response to various environmental signals remain less understood than those of bacterial flagella. T4P is also evolutionarily and structurally related to flagella in archaea, which have recently been designated archaella (8-11). Although newly developed techniques enable us to examine the dynamic properties of the machinery, little is known about the regulation mechanism of T4P because tens of components cooperate to orchestrate the dynamics of both the archaella and T4P system. Such complexity hampers the design of an experimental setup with quantitative and reproducible evaluations.To address how the T4P system is activated or repressed by environmental signals over a short timescale, we here used Synechocystis sp. PCC6803, a model cyanobacteria (12)(13)(14). This species exhibits T4P-dependent twitching motility on surfaces such as soft-agar plates at speeds of a few micrometers per minute, and the cell motility direction is regulated both posi...

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Section: Discussionmentioning

confidence: 96%

Asymmetric distribution of type IV pili triggered by directional light in unicellular cyanobacteria

Nakane

Nishizaka

2017

Proc. Natl. Acad. Sci. U.S.A.

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“…A similar gene architecture was found in pixD of Synechocystis sp. PCC 6803 (Yuan & Bauer, 2008) and papB of Rhodopseudomonas palustris (Kanazawa et al, 2010). In this last strain biofilm formation is regulated via a bluelight-dependent modulation of the cellular c-di-GMP level, mediated by protein-protein interaction between the short BLUF-domain-containing protein, PapB, and the EALdomain-containing protein, PapA.…”

Section: Discussion Genomics Analysesmentioning

confidence: 99%

Blue-light-dependent inhibition of twitching motility in Acinetobacter baylyi ADP1: additive involvement of three BLUF-domain-containing proteins

et al. 2013

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“…Recently, it was reported that Synechocystis PixD (PixD, Slr1694), which regulates phototactic movement of the cyanobacterial cell, also forms a decamer in the presence of the response regulator PixE (PixD 10 -PixE 5 complex) in solution in the dark state. 7 The complex was found to disassemble into a PixD dimer and a PixE monomer upon blue light irradiation. 7 For an understanding of the molecular mechanism of the light signal transduction of PixD, the photochemical reaction dynamics, including the changes in the protein conformation and/or interprotein interactions, should be clarified.…”

Section: Introductionmentioning

confidence: 99%

“…7 The complex was found to disassemble into a PixD dimer and a PixE monomer upon blue light irradiation. 7 For an understanding of the molecular mechanism of the light signal transduction of PixD, the photochemical reaction dynamics, including the changes in the protein conformation and/or interprotein interactions, should be clarified.…”

Section: Introductionmentioning

confidence: 99%

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

Tanaka

Nakasone

Okajima

et al. 2011

Journal of Molecular Biology

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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 (3.7×10(-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 (7.5×10(-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.

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PixE promotes dark oligomerization of the BLUF photoreceptor PixD

Cited by 63 publications

References 24 publications

Asymmetric distribution of type IV pili triggered by directional light in unicellular cyanobacteria

Asymmetric distribution of type IV pili triggered by directional light in unicellular cyanobacteria

Blue-light-dependent inhibition of twitching motility in Acinetobacter baylyi ADP1: additive involvement of three BLUF-domain-containing proteins

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

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