Analysis of the role of phosphorylcholine in Neisseria meningitidis
| Autor: | Matthew J. Warren |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Phase variation
genetic structures biology Phosphorylcholine Chemistry Neisseria meningitidis Virulence CHOP medicine.disease_cause biology.organism_classification eye diseases Pilus Microbiology immune system diseases hemic and lymphatic diseases Pilin polycyclic compounds medicine biology.protein Neisseria |
| Popis: | Pili of pathogenic Neisseria are major virulence factors associated with adhesion, cytotoxicity, twitching motility, autoaggregation and DNA transformation. Pili are important in contributing to the host specificity of N meningitidis. Pili are post- translationally modified by several di fferent modifications including the addition of phosphorylcholine (ChoP) and a pilin-linked glycan.ChoP is found on the surface structures of many pathogenic and commensal organisms of the respiratory tract. ChoP is attached to sugar moieties in Streptococcus pneumoniae, Haemophilus influenzae, and commensal Neisseria (teichoic acid, lipoteichoic acid and LPS). In these organisms, ChoP is important for the colonisation of the nasopharynx and invasion of the epithelium. Expression of ChoP is often subject to phase variation (high frequency on/off switching). The absence of ChoP is important for survival of the bacteria in the blood. In pathogenic Neisseria ChoP is covalently-linked to the pilus subunit protein, pilin.This thesis describes the identification and subsequent analysis of several ORFs homologous to genes involved in the biosynthesis or attachment of ChoP and similar compounds in other organisms. These homologues were insertionally inactivated in N meningitidis strain C311 #3. Western immunoblots of pilin with the ChoP specific mAb TEPC-15 showed that the ORF NMB0415, now referred to as pptA (Pilin Phosphorylcholine Transferase A), is involved in the addition of ChoP to pilin in N. meningitidis. In N menmgitidis pptA contains a homopolymeric tract of guanosine repeats. Sequencing of this tract from previously isolated ChoP phase variants showed that the loss of ChoP in these phase variants correlated with changes to the length of this repeat. These changes to the tract resulted in a frame-shift in pptA and thus its premature termination demonstrating pptA is responsible for the phase variable addition of ChoP in N. meningitidis.The variation in ChoP presence and accessibility is possibly important in the disease process. Therefore, the variation of ChoP accessibility was analysed using the mAb TEPC-15 on both native and denatured pili, by colony and western immunoblots respectively. These immunoblots showed that ChoP is surface exposed. They also showed that accessibility of the mAb TEPC-15 to ChoP is gready increased in some colonies. The increased accessibility to ChoP was analysed in these variants and it was found th at the accessibility of ChoP to the mAb is variable dependent on other pilin modifications and changes to the pilin monomer.n n n |
| Databáze: | OpenAIRE |
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