The Molecular Mechanism of Nitrate Chemotaxis via Direct Ligand Binding to the PilJ Domain of McpN

ABSTRACT Chemotaxis and energy taxis permit directed bacterial movements in gradients of environmental cues. Nitrate is a final electron acceptor for anaerobic respiration and can also serve as a nitrogen source for aerobic growth. Previous studies indicated that bacterial nitrate taxis is mediated...

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Autores principales:	David Martín-Mora, Álvaro Ortega, Miguel A. Matilla, Sergio Martínez-Rodríguez, José A. Gavira, Tino Krell
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2019
Materias:	Pseudomonas aeruginosa chemoreceptor chemotaxis nitrate Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/9c0eb4659db24ef3ae74d6fdb0492bc9
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spelling	oai:doaj.org-article:9c0eb4659db24ef3ae74d6fdb0492bc92021-11-15T15:55:13ZThe Molecular Mechanism of Nitrate Chemotaxis via Direct Ligand Binding to the PilJ Domain of McpN10.1128/mBio.02334-182150-7511https://doaj.org/article/9c0eb4659db24ef3ae74d6fdb0492bc92019-02-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.02334-18https://doaj.org/toc/2150-7511ABSTRACT Chemotaxis and energy taxis permit directed bacterial movements in gradients of environmental cues. Nitrate is a final electron acceptor for anaerobic respiration and can also serve as a nitrogen source for aerobic growth. Previous studies indicated that bacterial nitrate taxis is mediated by energy taxis mechanisms, which are based on the cytosolic detection of consequences of nitrate metabolism. Here we show that Pseudomonas aeruginosa PAO1 mediates nitrate chemotaxis on the basis of specific nitrate sensing by the periplasmic PilJ domain of the PA2788/McpN chemoreceptor. The presence of nitrate reduced mcpN transcript levels, and McpN-mediated taxis occurred only under nitrate starvation conditions. In contrast to the NarX and NarQ sensor kinases, McpN bound nitrate specifically and showed no affinity for other ligands such as nitrite. We report the three-dimensional structure of the McpN ligand binding domain (LBD) at 1.3-Å resolution in complex with nitrate. Although structurally similar to 4-helix bundle domains, the ligand binding mode differs since a single nitrate molecule is bound to a site on the dimer symmetry axis. As for 4-helix bundle domains, ligand binding stabilized the McpN-LBD dimer. McpN homologues showed a wide phylogenetic distribution, indicating that nitrate chemotaxis is a widespread phenotype. These homologues were particularly abundant in bacteria that couple sulfide/sulfur oxidation with nitrate reduction. This work expands the range of known chemotaxis effectors and forms the basis for the exploration of nitrate chemotaxis in other bacteria and for the study of its physiological role. IMPORTANCE Nitrate is of central importance in bacterial physiology. Previous studies indicated that movements toward nitrate are due to energy taxis, which is based on the cytosolic sensing of consequences of nitrate metabolism. Here we present the first report on nitrate chemotaxis. This process is initiated by specific nitrate binding to the periplasmic ligand binding domain (LBD) of McpN. Nitrate chemotaxis is highly regulated and occurred only under nitrate starvation conditions, which is helpful information to explore nitrate chemotaxis in other bacteria. We present the three-dimensional structure of the McpN-LBD in complex with nitrate, which is the first structure of a chemoreceptor PilJ-type domain. This structure reveals striking similarities to that of the abundant 4-helix bundle domain but employs a different sensing mechanism. Since McpN homologues show a wide phylogenetic distribution, nitrate chemotaxis is likely a widespread phenomenon with importance for the life cycle of ecologically diverse bacteria.David Martín-MoraÁlvaro OrtegaMiguel A. MatillaSergio Martínez-RodríguezJosé A. GaviraTino KrellAmerican Society for MicrobiologyarticlePseudomonas aeruginosachemoreceptorchemotaxisnitrateMicrobiologyQR1-502ENmBio, Vol 10, Iss 1 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	Pseudomonas aeruginosa chemoreceptor chemotaxis nitrate Microbiology QR1-502
spellingShingle	Pseudomonas aeruginosa chemoreceptor chemotaxis nitrate Microbiology QR1-502 David Martín-Mora Álvaro Ortega Miguel A. Matilla Sergio Martínez-Rodríguez José A. Gavira Tino Krell The Molecular Mechanism of Nitrate Chemotaxis via Direct Ligand Binding to the PilJ Domain of McpN
description	ABSTRACT Chemotaxis and energy taxis permit directed bacterial movements in gradients of environmental cues. Nitrate is a final electron acceptor for anaerobic respiration and can also serve as a nitrogen source for aerobic growth. Previous studies indicated that bacterial nitrate taxis is mediated by energy taxis mechanisms, which are based on the cytosolic detection of consequences of nitrate metabolism. Here we show that Pseudomonas aeruginosa PAO1 mediates nitrate chemotaxis on the basis of specific nitrate sensing by the periplasmic PilJ domain of the PA2788/McpN chemoreceptor. The presence of nitrate reduced mcpN transcript levels, and McpN-mediated taxis occurred only under nitrate starvation conditions. In contrast to the NarX and NarQ sensor kinases, McpN bound nitrate specifically and showed no affinity for other ligands such as nitrite. We report the three-dimensional structure of the McpN ligand binding domain (LBD) at 1.3-Å resolution in complex with nitrate. Although structurally similar to 4-helix bundle domains, the ligand binding mode differs since a single nitrate molecule is bound to a site on the dimer symmetry axis. As for 4-helix bundle domains, ligand binding stabilized the McpN-LBD dimer. McpN homologues showed a wide phylogenetic distribution, indicating that nitrate chemotaxis is a widespread phenotype. These homologues were particularly abundant in bacteria that couple sulfide/sulfur oxidation with nitrate reduction. This work expands the range of known chemotaxis effectors and forms the basis for the exploration of nitrate chemotaxis in other bacteria and for the study of its physiological role. IMPORTANCE Nitrate is of central importance in bacterial physiology. Previous studies indicated that movements toward nitrate are due to energy taxis, which is based on the cytosolic sensing of consequences of nitrate metabolism. Here we present the first report on nitrate chemotaxis. This process is initiated by specific nitrate binding to the periplasmic ligand binding domain (LBD) of McpN. Nitrate chemotaxis is highly regulated and occurred only under nitrate starvation conditions, which is helpful information to explore nitrate chemotaxis in other bacteria. We present the three-dimensional structure of the McpN-LBD in complex with nitrate, which is the first structure of a chemoreceptor PilJ-type domain. This structure reveals striking similarities to that of the abundant 4-helix bundle domain but employs a different sensing mechanism. Since McpN homologues show a wide phylogenetic distribution, nitrate chemotaxis is likely a widespread phenomenon with importance for the life cycle of ecologically diverse bacteria.
format	article
author	David Martín-Mora Álvaro Ortega Miguel A. Matilla Sergio Martínez-Rodríguez José A. Gavira Tino Krell
author_facet	David Martín-Mora Álvaro Ortega Miguel A. Matilla Sergio Martínez-Rodríguez José A. Gavira Tino Krell
author_sort	David Martín-Mora
title	The Molecular Mechanism of Nitrate Chemotaxis via Direct Ligand Binding to the PilJ Domain of McpN
title_short	The Molecular Mechanism of Nitrate Chemotaxis via Direct Ligand Binding to the PilJ Domain of McpN
title_full	The Molecular Mechanism of Nitrate Chemotaxis via Direct Ligand Binding to the PilJ Domain of McpN
title_fullStr	The Molecular Mechanism of Nitrate Chemotaxis via Direct Ligand Binding to the PilJ Domain of McpN
title_full_unstemmed	The Molecular Mechanism of Nitrate Chemotaxis via Direct Ligand Binding to the PilJ Domain of McpN
title_sort	molecular mechanism of nitrate chemotaxis via direct ligand binding to the pilj domain of mcpn
publisher	American Society for Microbiology
publishDate	2019
url	https://doaj.org/article/9c0eb4659db24ef3ae74d6fdb0492bc9
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The Molecular Mechanism of Nitrate Chemotaxis via Direct Ligand Binding to the PilJ Domain of McpN

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