Abstract
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.
Highlights
One of the environmental implications of industrialization has been the contamination of water sources with heavy metals either directly or indirectly [1]
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 biosynthesis glycosyltransferase (BshA), a UDP-GlcNAc transferase, as a structural template, several Neisseria meningitidis serogroup W (NmW) active site residues were identified as mutational targets to accommodate the proposed N-acetyl group in UDP-GalNAc
Summary
One of the environmental implications of industrialization has been the contamination of water sources with heavy metals either directly (i.e., industrial wastes) or indirectly (i.e., through contaminated soils) [1]. Gram-negative bacteria, have capsular polysaccharides that are firmly attached to the outer surface [4,5]. Capsular polysaccharides exhibit great diversity between bacteria in terms of the constituent monosaccharides, glycosidic linkages, and chemical modifications. They offer a rich source of diverse polysaccharides that could be further developed as biomaterials with varied applications [6]. This diversity underlies the pathogenicity of the Gram-negative bacteria Neisseria meningitidis [7], and our focus is on the capsular polysaccharide of serogroup W (NmW) [8,9]
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