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Solution structures of RseA and its complex with RseB.

Jin KS, Kim DY, Rho Y, Le VB, Kwon E, Kim KK, Ree M - J Synchrotron Radiat (2008)

Bottom Line: However, upon the formation of the stable complex with RseB, RseA induces conformational changes in RseB and, at the same time, RseA becomes more structured.Furthermore, it appears that some other undefined region of RseA, as well as the previously identified minimum region (amino acid 169-186), is also involved in RseB binding.It is thought that these conformational changes are relevant to the proteolytic cleavage of RseA and the modulation of envelope stress response.

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Affiliation: Department of Chemistry, National Research Laboratory for Polymer Synthesis and Physics, Pohang Accelerator Laboratory, Center for Integrated Molecular Systems, Polymer Research Institute, Pohang 790-784, Republic of Korea.

ABSTRACT
The bacterial envelope stress response, which is responsible for sensing stress signals in the envelope and for turning on the sigma(E)-dependent transcription, is modulated by the binding of RseB to RseA. In this study, the solution structures of RseA and its complex with RseB were analyzed using circular dichroism and small-angle X-ray scattering. The periplasmic domain of RseA is unstructured and flexible when it is not bound to RseB. However, upon the formation of the stable complex with RseB, RseA induces conformational changes in RseB and, at the same time, RseA becomes more structured. Furthermore, it appears that some other undefined region of RseA, as well as the previously identified minimum region (amino acid 169-186), is also involved in RseB binding. It is thought that these conformational changes are relevant to the proteolytic cleavage of RseA and the modulation of envelope stress response.

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Experimental SAXS data for RseB, RseA121–216, RseA169–186, RseA121–216/RseB and RseA169–196/RseB are depicted by (a) Guinier plots and (b) Kratky plots along q                  2 and q, respectively. Each plot is shifted along the vertical axis for clarity. (c) The distance distribution function p(r) of each protein was obtained from the experimental SAXS data. The plot of RseA169–196 is drawn in the upper right panel in magnified scale.
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fig1: Experimental SAXS data for RseB, RseA121–216, RseA169–186, RseA121–216/RseB and RseA169–196/RseB are depicted by (a) Guinier plots and (b) Kratky plots along q 2 and q, respectively. Each plot is shifted along the vertical axis for clarity. (c) The distance distribution function p(r) of each protein was obtained from the experimental SAXS data. The plot of RseA169–196 is drawn in the upper right panel in magnified scale.

Mentions: The Guinier plots of the measured SAXS data revealed various conformational forms of truncated RseAs, RseB and RseA/RseB complexes (Fig. 1 ▶ a). In the Guinier plots, except for RseA121–216, each scattering curve is well fitted to a straight line, indicating that the protein is considerably homogeneous in terms of the conformation. The radius of gyration (R g,G) was estimated from the slope value of the regression line within the Guinier region shown in Fig. 1 ▶(a). The determined R g,G values increase in the order RseA169–186 < RseA121–216/RseB < RseB ≃ RseA169–196/RseB (Table 1 ▶). Interestingly, the RseA121–216/RseB complex has a smaller R g,G value than the unbound RseB. This indicates that RseB is less flexible in the RseA-bound state than in the free state, which might be attributed to its conformation being fixed by the binding of RseA to the open grooves, as previously reported (Kim et al., 2007 ▶). The scattering profile of RseA121–216 showed a steep slope toward q = 0 (Fig. 1 ▶ a), indicative of the presence of a large diversity in size and conformation, that is, the fully unstructured state of the periplasmic domain of RseA. In contrast, RseA169–186 appears to be more homogeneous in conformation, which is probably a result of its small size.


Solution structures of RseA and its complex with RseB.

Jin KS, Kim DY, Rho Y, Le VB, Kwon E, Kim KK, Ree M - J Synchrotron Radiat (2008)

Experimental SAXS data for RseB, RseA121–216, RseA169–186, RseA121–216/RseB and RseA169–196/RseB are depicted by (a) Guinier plots and (b) Kratky plots along q                  2 and q, respectively. Each plot is shifted along the vertical axis for clarity. (c) The distance distribution function p(r) of each protein was obtained from the experimental SAXS data. The plot of RseA169–196 is drawn in the upper right panel in magnified scale.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2394797&req=5

fig1: Experimental SAXS data for RseB, RseA121–216, RseA169–186, RseA121–216/RseB and RseA169–196/RseB are depicted by (a) Guinier plots and (b) Kratky plots along q 2 and q, respectively. Each plot is shifted along the vertical axis for clarity. (c) The distance distribution function p(r) of each protein was obtained from the experimental SAXS data. The plot of RseA169–196 is drawn in the upper right panel in magnified scale.
Mentions: The Guinier plots of the measured SAXS data revealed various conformational forms of truncated RseAs, RseB and RseA/RseB complexes (Fig. 1 ▶ a). In the Guinier plots, except for RseA121–216, each scattering curve is well fitted to a straight line, indicating that the protein is considerably homogeneous in terms of the conformation. The radius of gyration (R g,G) was estimated from the slope value of the regression line within the Guinier region shown in Fig. 1 ▶(a). The determined R g,G values increase in the order RseA169–186 < RseA121–216/RseB < RseB ≃ RseA169–196/RseB (Table 1 ▶). Interestingly, the RseA121–216/RseB complex has a smaller R g,G value than the unbound RseB. This indicates that RseB is less flexible in the RseA-bound state than in the free state, which might be attributed to its conformation being fixed by the binding of RseA to the open grooves, as previously reported (Kim et al., 2007 ▶). The scattering profile of RseA121–216 showed a steep slope toward q = 0 (Fig. 1 ▶ a), indicative of the presence of a large diversity in size and conformation, that is, the fully unstructured state of the periplasmic domain of RseA. In contrast, RseA169–186 appears to be more homogeneous in conformation, which is probably a result of its small size.

Bottom Line: However, upon the formation of the stable complex with RseB, RseA induces conformational changes in RseB and, at the same time, RseA becomes more structured.Furthermore, it appears that some other undefined region of RseA, as well as the previously identified minimum region (amino acid 169-186), is also involved in RseB binding.It is thought that these conformational changes are relevant to the proteolytic cleavage of RseA and the modulation of envelope stress response.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, National Research Laboratory for Polymer Synthesis and Physics, Pohang Accelerator Laboratory, Center for Integrated Molecular Systems, Polymer Research Institute, Pohang 790-784, Republic of Korea.

ABSTRACT
The bacterial envelope stress response, which is responsible for sensing stress signals in the envelope and for turning on the sigma(E)-dependent transcription, is modulated by the binding of RseB to RseA. In this study, the solution structures of RseA and its complex with RseB were analyzed using circular dichroism and small-angle X-ray scattering. The periplasmic domain of RseA is unstructured and flexible when it is not bound to RseB. However, upon the formation of the stable complex with RseB, RseA induces conformational changes in RseB and, at the same time, RseA becomes more structured. Furthermore, it appears that some other undefined region of RseA, as well as the previously identified minimum region (amino acid 169-186), is also involved in RseB binding. It is thought that these conformational changes are relevant to the proteolytic cleavage of RseA and the modulation of envelope stress response.

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