Determination of the binding affinities of Neisseria meningitidis serogroup W capsule polymerase with two nucleotide sugar substrates

Towards Computationally Guided Design and Engineering of a Neisseria meningitidis Serogroup W Capsule Polymerase with Altered Substrate Specificity

Heavy metal contamination of drinking water is a public health concern that requires the development of more efficient bioremediation techniques. Absorption technologies, including biosorption, provide opportunities for improvements to increase the diversity of target metal ions and overall binding capacity. Microorganisms are a key component in wastewater treatment plants, and they naturally bind metal ions through surface macromolecules but with limited capacity. The long-term goal of this work is to engineer capsule polymerases to synthesize molecules with novel functionalities. In previously published work, we showed that the Neisseria meningitidis serogroup W (NmW) galactose-sialic acid (Gal-NeuNAc) heteropolysaccharide binds lead ions effectively, thereby demonstrating the potential for its use in environmental decontamination applications. In this study, computational analysis of the NmW capsule polymerase galactosyltransferase (GT) domain was used to gain insight into how the enzyme could be modified to enable the synthesis of N-acetylgalactosamine-sialic acid (GalNAc-NeuNAc) heteropolysaccharide. Various computational approaches, including molecular modeling with I-TASSER and molecular dynamics (MD) simulations with NAMD, were utilized to identify key amino acid residues in the substrate binding pocket of the GT domain that may be key to conferring UDP-GalNAc specificity. Through these combined strategies and using BshA, a UDP-GlcNAc transferase, as a structural template, several NmW active site residues were identified as mutational targets to accommodate the proposed N-acetyl group in UDP-GalNAc. Thus, a rational approach for potentially conferring new properties to bacterial capsular polysaccharides is demonstrated.

Investigation of bioluminescence-based assays for determination of kinetic parameters for the bifunctional Neisseria meningitidis serogroup W capsule polymerase

Objective

Neisseria meningitidis is a Gram-negative bacterium that causes meningitis. N. meningitidis serogroup W (NmW) capsule polymerase synthesizes capsular polysaccharide of this serogroup. This enzyme could be a tool for meningococcal glycoconjugate vaccine development. Our long-term goal is to control activity of the NmW capsule polymerase for production of defined carbohydrates for vaccines. The enzyme lacks a simple, high-throughput activity assay. Here, we describe the use of high-throughput bioluminescence assays (CMP-Glo and UDP-Glo by Promega) to investigate NmW capsule polymerase activity. These assays detect free nucleotides produced during transfer of sugar from UDP-Galactose and CMP-Sialic Acid to an acceptor. Kinetic studies using NmW hydrolyzed polysaccharide (PS) acceptor are described as well as preliminary work with a sialic acid trimer (DP3) acceptor.

Results

In CMP-Glo kinetic studies, with constant donor (80 µM) and varied NmW hydrolyzed polysaccharide (0–2000 µg/mL), a K_m of 629.2 ± 101.4 µg/mL and a V_max of 0.8965 ± 0.05823 µM/min was obtained. Using UDP-Glo, K_m and V_max values of 13.84 ± 9.675 µM and 0.6205 ± 0.1331 µM/min were obtained with varied CMP-NeuNAc (0–80 µM) and constant acceptor (400 µg/mL) and UDP-Gal (80 µM). This is the first report of using bioluminescence assays for NmW kinetics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05831-1.

Recent and Future Advances in the Chemoenzymatic Synthesis of Homogeneous Glycans for Bacterial Glycoconjugate Vaccine Development

Vaccines are important in preventing disease outbreaks and controlling the spread of disease in a population. A variety of vaccines exist, including subunit, recombinant, and conjugate vaccines. Glycoconjugate vaccines have been an important tool to fight against diseases caused by a number of bacteria. Glycoconjugate vaccines are often heterogeneous. Vaccines of the future are becoming more rationally designed to have a defined oligosaccharide chain length and position of conjugation. Homogenous vaccines could play an important role in assessing the relationship between vaccine structure and immune response. This review focuses on recent advances in the chemoenzymatic production of defined bacterial oligosaccharides for vaccine development with a focus on Neisseria meningitidis and selected WHO-prioritized antibacterial resistant-pathogens. We also provide some perspective on future advances in the chemoenzymatic synthesis of well-defined oligosaccharides.

Comparative transcriptomics analysis of Streptococcus mutans with disruption of LuxS/AI-2 quorum sensing and recovery of methyl cycle

OBJECTIVE

The LuxS/AI-2 quorum sensing (QS) system has critical roles in Streptococcus mutans cariogenicity. Whereas the molecular and cellular mechanisms of the LuxS/AI-2 QS system are not thoroughly understood. Given that LuxS has roles in QS and methyl cycle, its mutation can cause QS deficiency and methyl cycle disruption. The aim of this study was to investigate effects of the LuxS/AI-2 QS system on gene expression in Streptococcus mutans when methyl cycle was recovered with exogenous sahH gene.

METHODS

Our previous study introduced the exogenous sahH gene from Pseudomonas aeruginosa into an S. mutans luxS-null strain to restore the disrupted methyl cycle, and this produced the solely the LuxS/AI-2 QS system deficient strain. Here, we analyzed the transcriptomics of this strain to get insights into the molecular mechanisms of the LuxS/AI-2 QS system applying RNA-seq.

RESULTS

With recovery of methyl cycle, 84 genes didn't change in expression trends in S. mutans luxS-null strain. These genes mainly encode the ABC transporters, sugar transporter EII and enzymes of carbohydrate metabolism, and are rich in the Phosphotransferase system, Fructose and mannose metabolism, Amino sugar and nucleotide sugar metabolism, Galactose metabolism, Glycolysis/Gluconeogenesis, RNA degradation, Lysine biosynthesis, and Glycine, serine and threonine metabolism.

CONCLUSIONS

The LuxS/AI-2 QS system may mainly affect ABC transporters and carbohydrate transport, transformation and metabolism via EII subunits and enzymes to influence virulence-associated traits without effects of methyl cycle inStreptococcus mutans.