Dataset Information

A Proline-Rich Element in the Type III Secretion Protein FlhB Contributes to Flagellar Biogenesis in the Beta- and Gamma-Proteobacteria.

ABSTRACT: Flagella are bacterial organelles of locomotion. Their biogenesis is highly coordinated in time and space and relies on a specialized flagellar type III secretion system (fT3SS) required for the assembly of the extracellular hook, rod, and filament parts of this complex motor device. The fT3SS protein FlhB switches secretion substrate specificity once the growing hook reaches its determined length. Here we present the crystal structure of the cytoplasmic domain of the transmembrane protein FlhB. The structure visualizes a so-far unseen proline-rich region (PRR) at the very C-terminus of the protein. Strains lacking the PRR show a decrease in flagellation as determined by hook- and filament staining, indicating a role of the PRR during assembly of the hook and filament structures. Phylogenetic analysis shows that the PRR is a primary feature of FlhB proteins of flagellated beta- and gamma-proteobacteria. Taken together, our study adds another layer of complexity and organismic diversity to the process of flagella biogenesis.

SUBMITTER: Hook JC

PROVIDER: S-EPMC7771051 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Publications

A Proline-Rich Element in the Type III Secretion Protein FlhB Contributes to Flagellar Biogenesis in the Beta- and Gamma-Proteobacteria.

Hook John C JC Blagotinsek Vitan V Pané-Farré Jan J Mrusek Devid D Altegoer Florian F Dornes Anita A Schwan Meike M Schier Lukas L Thormann Kai M KM Bange Gert G

Frontiers in microbiology 20201215

Flagella are bacterial organelles of locomotion. Their biogenesis is highly coordinated in time and space and relies on a specialized flagellar type III secretion system (fT3SS) required for the assembly of the extracellular hook, rod, and filament parts of this complex motor device. The fT3SS protein FlhB switches secretion substrate specificity once the growing hook reaches its determined length. Here we present the crystal structure of the cytoplasmic domain of the transmembrane protein FlhB. ...[more]

PMID: 33384667

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Project description:The bacterial type III export apparatus is found in the flagellum and in the needle complex of some pathogenic Gram-negative bacteria. In the needle complex its function is to secrete effector proteins for infection into Eukaryotic cells. In the bacterial flagellum it exports specific proteins for the building of the flagellum during its assembly. The export apparatus is composed of about five membrane proteins and three soluble proteins. The mechanism of the export apparatus is not fully understood. The five membrane proteins are well conserved and essential. Here a cross-complementation assay was performed: substituting in the flagellar system of Salmonella one of these membrane proteins, FlhB, by the FlhB ortholog from Aquifex aeolicus (an evolutionary distant hyperthermophilic bacteria) or a chimeric protein (AquSalFlhB) made by the combination of the trans-membrane domain of A. aeolicus FlhB with the cytoplasmic domain of Salmonella FlhB dramatically reduced numbers of flagella and motility. From cells expressing the chimeric AquSalFlhB protein, suppressor mutants with enhanced motility were isolated and the mutations were identified using whole genome sequencing. Gain-of-function mutations were found in the gene encoding FlhA, another membrane protein of the type III export apparatus. Also, mutations were identified in genes encoding 4-hydroxybenzoate octaprenyltransferase, ubiquinone/menaquinone biosynthesis methyltransferase, and 4-hydroxy-3-methylbut-2-en-1-yl diphosphate synthase, which are required for ubiquinone biosynthesis. The mutations were shown by reversed-phase high performance liquid chromatography to reduce the quinone pool of the cytoplasmic membrane. Ubiquinone biosynthesis could be restored for the strain bearing a mutated gene for 4-hydroxybenzoate octaprenyltransferase by the addition of excess exogenous 4-hydroxybenzoate. Restoring the level of ubiquinone reduced flagella biogenesis with the AquSalFlhB chimera demonstrating that the respiratory chain quinone pool is responsible for this phenomenon.

Dataset Information

A Proline-Rich Element in the Type III Secretion Protein FlhB Contributes to Flagellar Biogenesis in the Beta- and Gamma-Proteobacteria.

Publications

A Proline-Rich Element in the Type III Secretion Protein FlhB Contributes to Flagellar Biogenesis in the Beta- and Gamma-Proteobacteria.

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