Host glycan degradation by Streptococcus pneumoniae
| dc.contributor.author | Cid, Melissa | |
| dc.contributor.supervisor | Boraston, Alisdair Bennett | |
| dc.date.accessioned | 2015-08-25T22:54:52Z | |
| dc.date.available | 2016-07-17T11:22:07Z | |
| dc.date.copyright | 2015 | en_US |
| dc.date.issued | 2015-08-25 | |
| dc.degree.department | Department of Biochemistry and Microbiology | |
| dc.degree.level | Doctor of Philosophy Ph.D. | en_US |
| dc.description.abstract | Streptococcus pneumoniae is a commensal inhabitant of the human nasopharynx that can sometimes become pathogenic and cause diseases such as pneumonia, otitis media and meningitis. Carbohydrate metabolism is a critical component of S. pneumoniae virulence. Among the myriad of carbohydrate-specific pathways involved in the host-pneumococcus interaction, the N-glycan foraging pathway stands out because of its direct implication in numerous aspects of virulence such as fitness, adhesion/invasion and impairment of the host immune response. Much of the literature has been focussed on the importance of step-wise depolymerisation of N-glycans by the enzymes NanA, BgaA and StrH. However, the importance of the liberation of N-glycans from host glycoconjuguates and their intake by the bacterium has yet to be examined. We have identified a Carbohydrate Processing Locus (CPL) that is highly conserved throughout a large number of Firmicutes and whose individual components appear widespread in bacteria that we hypothesize is active on host N-glycans. This locus encodes for two putative α-mannosidases GH92 and GH38, a characterised α-mannosidase GH125, a putative β-hexosaminidase GH20C, a putative α-fucosidase GH29 and a ROK (Repressor, Open reading frame, Kinase) protein. The genomic context of CPL orthologues suggests that an endo-β-N-acetylglucosaminidase (EndoD) and an ABC transporter (ABCN-glycan) are functionally associated with this locus. Based on our bioinformatic analyses and known functions of these proteins we hypothesize that the CPL encodes a concerted pathway responsible for the liberation, transport, and processing of N-glycans. The objective of this research is to characterize the putative components of this pathway and assess their implication in virulence. Specific focus on ABCN-glycan demonstrated its specificity for a range of N-glycans liberated by EndoD, shedding light on a novel import system for branched N-glycans. Furthermore, we provided evidence that GH92 is an α-1,2-mannosidase that likely removes the terminal mannose residues found on high-mannose N-glycans. EndoD and GH92 are shown to participate in virulence in mice; however, their role in virulence has yet to be determined. This work will significantly advance the construction and validation of a model of N-glycan processing by S. pneumoniae. As the components of this model pathway are conserved amongst a wide variety of bacteria, this work is of fundamental relevance to understanding how microbes from various environments degrade and metabolize N-glycans. | en_US |
| dc.description.scholarlevel | Graduate | en_US |
| dc.identifier.uri | http://hdl.handle.net/1828/6554 | |
| dc.language | English | eng |
| dc.language.iso | en | en_US |
| dc.rights | Available to the World Wide Web | en_US |
| dc.subject | Streptococcus pneumoniae | en_US |
| dc.subject | Glycoside hydrolase | en_US |
| dc.subject | host glycan | en_US |
| dc.subject | N-glycan | en_US |
| dc.subject | Carbohydrate | en_US |
| dc.subject | virulence | en_US |
| dc.title | Host glycan degradation by Streptococcus pneumoniae | en_US |
| dc.type | Thesis | en_US |