Session: General Posters:

Neisseria meningitidis is a gram-negative bacterium that causes an invasive meningococcal disease (IMD) in humans. The polysaccharide-rich capsules surrounding gram-negative bacteria play many physiological roles that influence virulence. Further, capsular polysaccharides may serve as a source of novel biopolymers. Although it is known that serogroup-specific capsule polymerases synthesize these polysaccharides, the biochemistry of these enzymes are not completely understood, which limits the ability to develop effective vaccines and therapeutics. There are few studies which focus on the structural biology and mechanisms of the Neisseria meningitidis serogroup W (NmW) capsule polymerase. This enzyme consists of N-terminal galactosyltransferase (GT) domain, an intervening sequence, and a C-terminal sialyltransferase (ST) domain which work together to create a galactose-sialic acid heteropolymer. This work focuses on understanding the structural determinants of substrate specificity of the GT domain of the NmW capsule polymerase through computational molecular modeling and molecular dynamic simulations. In the absence of experimentally determined atomic coordinates, a homology model was generated with I-TASSER. The structure was prepared for molecular dynamic simulations with CHARMM-GUI and equilibrated for 1.5ns, and production simulations were conducted for 99ns. Docking of UDP-Gal and UDP-GalNAc to the predicted homology model of the galactosyltransferase domain are being conducted with AUTODOCK. MD simulations of the ligand-free enzyme show significant fluctuations in key regions of the enzyme including a loop near but not within the active site (aa 38-44) and a more distant alpha-helical region (aa 205-221). Docking simulations with both the natural ligand and artificials are ongoing to visualize putative interactions and to inform further experiments. Further study of this enzyme can be beneficial for vaccine development and add value to ongoing research on novel polysaccharide synthesis for biomaterials applications.

Pumtiwitt McCarthy Ph.D.

Associate Professor and Interim Chairperson, Morgan State University

Appearances