6OVM

Crystal Structure of the Pseudomonas capeferrum Anti-sigma Regulator PupR C-terminal Cell-surface Signaling Domain in Complex with the Outer Membrane Transporter PupB N-terminal Signaling Domain (SeMet)

Summary for 6OVM

• Entry DOI: 10.2210/pdb6ovm/pdb
• Descriptor: Siderophore-interacting protein, Ferric-pseudobactin BN7/BN8 receptor, L(+)-TARTARIC ACID, ... (4 entities in total)
• Functional Keywords: signaling protein, transcriptional regulation, periplasmic protein, iron transport regulation
• Biological source: Pseudomonas capeferrum; More
• Total number of polymer chains: 2
• Total formula weight: 32746.06

Authors

Jensen, J.L.,Colbert, C.L. (deposition date: 2019-05-08, release date: 2020-03-04, Last modification date: 2024-10-16)

Primary citation

Jensen, J.L.,Jernberg, B.D.,Sinha, S.C.,Colbert, C.L.
Structural basis of cell-surface signaling by a conserved sigma regulator in Gram-negative bacteria.
J.Biol.Chem., 295:5795-5806, 2020

PubMed Abstract: Cell-surface signaling (CSS) in Gram-negative bacteria involves highly conserved regulatory pathways that optimize gene expression by transducing extracellular environmental signals to the cytoplasm via inner-membrane sigma regulators. The molecular details of ferric siderophore-mediated activation of the iron import machinery through a sigma regulator are unclear. Here, we present the 1.56 Å resolution structure of the periplasmic complex of the C-terminal CSS domain (CCSSD) of PupR, the sigma regulator in the pseudobactin BN7/8 transport system, and the N-terminal signaling domain (NTSD) of PupB, an outer-membrane TonB-dependent transducer. The structure revealed that the CCSSD consists of two subdomains: a juxta-membrane subdomain, which has a novel all-β-fold, followed by a secretin/TonB, short N-terminal subdomain at the C terminus of the CCSSD, a previously unobserved topological arrangement of this domain. Using affinity pulldown assays, isothermal titration calorimetry, and thermal denaturation CD spectroscopy, we show that both subdomains are required for binding the NTSD with micromolar affinity and that NTSD binding improves CCSSD stability. Our findings prompt us to present a revised model of CSS wherein the CCSSD:NTSD complex forms prior to ferric-siderophore binding. Upon siderophore binding, conformational changes in the CCSSD enable regulated intramembrane proteolysis of the sigma regulator, ultimately resulting in transcriptional regulation.

PubMed: 32107313
DOI: 10.1074/jbc.RA119.010697

Experimental method

X-RAY DIFFRACTION (1.6 Å)