Title:
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Studies on structure, function and immunogenicity of neisserial secreted protein Gly1ORF1
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Despite major advances in the field of meningococcal pathogenesis research in recent decades, Neisseria meningitidis still remains a leading cause of meningitis and septicaemia world-wide. The high mortality and morbidity rates of meningococcal infection drive further research towards identifying novel and more effective therapeutic measures. This study focuses on a small secreted protein found to have haem binding activity and an ability to interact with red blood cells. Gly1ORF1 protein is highly conserved and ubiquitous among the invasive strains of N. meningitidis. The crystal structure of the Gly1ORF1 K12A variant, solved in this study, showed that the protein possess a novel fold and is present in solution as a dimer. This study provides the first quantitative determination of Gly1ORF1 – haem interaction and has enabled the estimation of the dissociation constant for Gly1ORF1 variants. Gly1ORF1's role in iron acquisition was suggested by a previous study. Therefore, the haemoglobin receptor HmbR was expressed in E. coli and was tested for the interaction with Gly1ORF1. The preliminary data suggests that there is interaction between those proteins. Additionally, this study shows that Gly1ORF1 is immunogenic in man and animals and that antibodies against this protein are able to direct complement-mediated killing of N. meningitidis. A newly identified group of Gly1ORF1 homologs was also studied in this work. Two of the potential Gly1ORF1 homologs and one neisserial paralog were expressed in E. coli and subjected to functional analysis. The data suggest that the Gly1ORF1 homolog protein family is a group of small secreted proteins with shared secondary structure characteristics, but may have diverse functions. They might constitute a novel family of the bacterial virulence factors that could be novel therapeutic targets.
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