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Structural and functional analyses of the N-terminal domain of the A subunit of a Bacillus megaterium spore germinant receptor.

ABSTRACT: Germination of Bacillus spores is induced by the interaction of specific nutrient molecules with germinant receptors (GRs) localized in the spore's inner membrane. GRs typically consist of three subunits referred to as A, B, and C, although functions of individual subunits are not known. Here we present the crystal structure of the N-terminal domain (NTD) of the A subunit of the Bacillus megaterium GerK3 GR, revealing two distinct globular subdomains bisected by a cleft, a fold with strong homology to substrate-binding proteins in bacterial ABC transporters. Molecular docking, chemical shift perturbation measurement, and mutagenesis coupled with spore germination analyses support a proposed model that the interface between the two subdomains in the NTD of GR A subunits serves as the germinant binding site and plays a critical role in spore germination. Our findings provide a conceptual framework for understanding the germinant recruitment mechanism by which GRs trigger spore germination.

SUBMITTER: Li Y

PROVIDER: S-EPMC6561283 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Structural and functional analyses of the N-terminal domain of the A subunit of a Bacillus megaterium spore germinant receptor.

Li Yunfeng Y Jin Kai K Perez-Valdespino Abigail A Federkiewicz Kyle K Davis Andrew A Maciejewski Mark W MW Setlow Peter P Hao Bing B

Proceedings of the National Academy of Sciences of the United States of America 20190521 23

Germination of Bacillus spores is induced by the interaction of specific nutrient molecules with germinant receptors (GRs) localized in the spore's inner membrane. GRs typically consist of three subunits referred to as A, B, and C, although functions of individual subunits are not known. Here we present the crystal structure of the N-terminal domain (NTD) of the A subunit of the Bacillus megaterium GerK3 GR, revealing two distinct globular subdomains bisected by a cleft, ...[more]

PMID: 31113879

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Project description:The exosporium of Bacillus megaterium QM B1551 spores is morphologically distinct from exosporia observed for the spores of many other species. Previous work has demonstrated that unidentified genes carried on one of the large indigenous plasmids are required for the assembly of the Bacillus megaterium exosporium. Here, we provide evidence that pBM600-encoded orthologues of the Bacillus subtilis CotW and CotX proteins, which form the crust layer in spores of that species, are structural components of the Bacillus megaterium QM B1551 spore exosporium. The introduction of plasmid-borne cotW and orthologous cotX genes to the PV361 strain, which lacks all indigenous plasmids and produces spores that are devoid of an exosporium, results in the development of spores with a rudimentary exosporium-type structure. Additionally, purified recombinant CotW protein is shown to assemble at the air-water interface to form thin sheets of material, which is consistent with the idea that this protein may form a basal layer in the Bacillus megaterium QM B1551 exosporium.IMPORTANCE When starved of nutrients, some bacterial species develop metabolically dormant spores that can persist in a viable state in the environment for several years. The outermost layers of spores are of particular interest since (i) these represent the primary site for interaction with the environment and (ii) the protein constituents may have biotechnological applications. The outermost layer, or exosporium, in Bacillus megaterium QM B1551 spores is of interest, as it is morphologically distinct from the exosporia of spores of the pathogenic Bacillus cereus family. In this work, we provide evidence that structurally important protein constituents of the Bacillus megaterium exosporium are different from those in the Bacillus cereus family. We also show that one of these proteins, when purified, can assemble to form sheets of exosporium-like material. This is significant, as it indicates that spore-forming bacteria employ different proteins and mechanisms of assembly to construct their external layers.

Dataset Information

Structural and functional analyses of the N-terminal domain of the A subunit of a Bacillus megaterium spore germinant receptor.

Publications

Structural and functional analyses of the N-terminal domain of the A subunit of a <i>Bacillus megaterium</i> spore germinant receptor.

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