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Three structurally and functionally distinct β-glucuronidases from the human gut microbe Bacteroides uniformis.

ABSTRACT: The glycoside hydrolases encoded by the human gut microbiome play an integral role in processing a variety of exogenous and endogenous glycoconjugates. Here we present three structurally and functionally distinct β-glucuronidase (GUS) glycoside hydrolases from a single human gut commensal microbe, Bacteroides uniformis We show using nine crystal structures, biochemical, and biophysical data that whereas these three proteins share similar overall folds, they exhibit different structural features that create three structurally and functionally unique enzyme active sites. Notably, quaternary structure plays an important role in creating distinct active site features that are hard to predict via structural modeling methods. The enzymes display differential processing capabilities toward glucuronic acid-containing polysaccharides and SN-38-glucuronide, a metabolite of the cancer drug irinotecan. We also demonstrate that GUS-specific and nonselective inhibitors exhibit varying potencies toward each enzyme. Together, these data highlight the diversity of GUS enzymes within a single Bacteroides gut commensal and advance our understanding of how structural details impact the specific roles microbial enzymes play in processing drug-glucuronide and glycan substrates.

SUBMITTER: Pellock SJ

PROVIDER: S-EPMC6290157 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Three structurally and functionally distinct β-glucuronidases from the human gut microbe <i>Bacteroides uniformis</i>.

Pellock Samuel J SJ Walton William G WG Biernat Kristen A KA Torres-Rivera Dariana D Creekmore Benjamin C BC Xu Yongmei Y Liu Jian J Tripathy Ashutosh A Stewart Lance J LJ Redinbo Matthew R MR

The Journal of biological chemistry 20181009 48

The glycoside hydrolases encoded by the human gut microbiome play an integral role in processing a variety of exogenous and endogenous glycoconjugates. Here we present three structurally and functionally distinct β-glucuronidase (GUS) glycoside hydrolases from a single human gut commensal microbe, <i>Bacteroides uniformis</i> We show using nine crystal structures, biochemical, and biophysical data that whereas these three proteins share similar overall folds, they exhibit different structural fe ...[more]

PMID: 30301767

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Project description:Thiamine (vitamin B1) is an essential cofactor for all organisms. Humans primarily acquire thiamine through their diet, and thiamine deficiencies have adverse neurological effects. However, the role gut microbes play in modulating thiamine availability is poorly understood, and little is known about how thiamine impacts the stability of microbial gut communities. To investigate thiamine's role in the gut, we utilized the model gut microbe Bacteroides thetaiotaomicron. Transcriptome sequencing (RNA-seq) revealed a global downregulation of thiamine and amino acid biosynthesis, glycolysis, and purine metabolism when thiamine was present. Using genetic mutants with thiamine biosynthesis and transport locus mutations, we determined both systems were critical for growth in thiamine-deficient medium. The defect in the double transport mutant suggests an uncharacterized feedback mechanism between thiamine transport and biosynthesis in B. thetaiotaomicron. Mutant phenotypes were recapitulated during pairwise competitions, reinforcing the importance of encoding versatile thiamine acquisition mechanisms when thiamine concentrations are variable. In addition, liquid chromatography-mass spectrometry (LC-MS) analyses corroborate that exogenous thiamine levels affect the internal thiamine pool of B. thetaiotaomicron. Furthermore, we computationally examined the ability of other gut microbes to acquire thiamine and identified lineage-specific differences in thiamine acquisition strategies. Among the Bacteroidetes, the capacities for both thiamine transport and biosynthesis are common. Together, these data show that thiamine acquisition mechanisms used by B. thetaiotaomicron not only are critical for its physiology and fitness but also provide the opportunity to model how other gut microbes may respond to the shifting availability of thiamine in the gut. IMPORTANCE Variation in the ability of gut microbes to transport, synthesize, and compete for vitamin B1 (thiamine) is expected to impact the structure and stability of the microbiota, and ultimately this variation may have both direct and indirect effects on human health. Our study identifies the diverse strategies employed by gut Bacteroidetes to acquire thiamine. We demonstrate how the presence or absence of thiamine biosynthesis or transport dramatically affects the abundance of B. thetaiotaomicron in a competitive environment. This study adds further evidence that altering the presence or concentrations of water-soluble vitamins such as thiamine may be an effective method for manipulating gut community composition. In turn, targeted thiamine delivery could be used therapeutically to alter dysbiotic communities linked to disease. Author Video: An author video summary of this article is available.

Dataset Information

Three structurally and functionally distinct β-glucuronidases from the human gut microbe Bacteroides uniformis.

Publications

Three structurally and functionally distinct β-glucuronidases from the human gut microbe <i>Bacteroides uniformis</i>.

Similar Datasets

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