4HI4

Crystal structure of the 5-coordinate ferric heme-binding PAS domain of Aer2 from P. aeruginosa

Summary for 4HI4

• Entry DOI: 10.2210/pdb4hi4/pdb
• Related: 3LNR 3VOL
• Descriptor: Aerotaxis transducer Aer2, PROTOPORPHYRIN IX CONTAINING FE, CHLORIDE ION, ... (5 entities in total)
• Functional Keywords: pas domain, diatomic gas sensor, signaling protein
• Biological source: Pseudomonas aeruginosa
• Total number of polymer chains: 4
• Total formula weight: 56338.13

Authors

Airola, M.V.,Crane, B.R. (deposition date: 2012-10-11, release date: 2013-01-09, Last modification date: 2024-02-28)

Primary citation

Airola, M.V.,Huh, D.,Sukomon, N.,Widom, J.,Sircar, R.,Borbat, P.P.,Freed, J.H.,Watts, K.J.,Crane, B.R.
Architecture of the soluble receptor Aer2 indicates an in-line mechanism for PAS and HAMP domain signaling.
J.Mol.Biol., 425:886-901, 2013

PubMed Abstract: Bacterial receptors typically contain modular architectures with distinct functional domains that combine to send signals in response to stimuli. Although the properties of individual components have been investigated in many contexts, there is little information about how diverse sets of modules work together in full-length receptors. Here, we investigate the architecture of Aer2, a soluble gas-sensing receptor that has emerged as a model for PAS (Per-Arnt-Sim) and poly-HAMP (histidine kinase-adenylyl cyclase-methyl-accepting chemotaxis protein-phosphatase) domain signaling. The crystal structure of the heme-binding PAS domain in the ferric, ligand-free form, in comparison to the previously determined cyanide-bound state, identifies conformational changes induced by ligand binding that are likely essential for the signaling mechanism. Heme-pocket alternations share some similarities with the heme-based PAS sensors FixL and EcDOS but propagate to the Iβ strand in a manner predicted to alter PAS-PAS associations and the downstream HAMP junction within full-length Aer2. Small-angle X-ray scattering of PAS and poly-HAMP domain fragments of increasing complexity allow unambiguous domain assignments and reveal a linear quaternary structure. The Aer2 PAS dimeric crystal structure fits well within ab initio small-angle X-ray scattering molecular envelopes, and pulsed dipolar ESR measurements of inter-PAS distances confirm the crystallographic PAS arrangement within Aer2. Spectroscopic and pull-down assays fail to detect direct interactions between the PAS and HAMP domains. Overall, the Aer2 signaling mechanism differs from the Escherichia coli Aer paradigm, where side-on PAS-HAMP contacts are key. We propose an in-line model for Aer2 signaling, where ligand binding induces alterations in PAS domain structure and subunit association that is relayed through the poly-HAMP junction to downstream domains.

PubMed: 23274111
DOI: 10.1016/j.jmb.2012.12.011

Experimental method

X-RAY DIFFRACTION (2.304 Å)