Characterization of Phosphoglycerate Kinase Expressed on the Surface of Group B Streptococcus

• Author / Creator

  Boone, Tyler J

• Group B streptococcus (GBS) is a major cause of invasive disease in the neonatal and adult populations. To mediate invasive disease, GBS encodes a variety of surface expressed and secreted components. One surface expressed protein that may contribute to GBS virulence is phosphoglycerate kinase (PGK; a glycolytic enzyme). Glycolytic enzymes have been identified on the surface of many Gram positive bacteria, despite the absence of any known secretion or surface attachment signal. My results demonstrate that the SecA2 locus, in particular the Srr1 fimbrial protein, is required for transport of PGK across the GBS membrane. Once across the bacterial membrane, PGK becomes attached to the bacterial surface through interaction with lipoteichoic acid as well as a second ligand that also requires Srr1 for expression. While the surface localization of PGK suggests it may play a role in GBS virulence, confirming their role in virulence has been hampered by its role in glycolysis. Due to the essential cytoplasmic role of PGK in metabolism, traditional knock-out mutagenesis is not possible to determine its function on the bacterial surface. My results demonstrate that GBS-PGK may contribute to GBS virulence through its ability to bind to actin, fibrin, fibrinogen, fibronectin and plasminogen. Site directed mutagenesis, preventing interaction with host proteins without affecting the glycolytic activity, has previously been used to demonstrate a role for the glycolytic enzymes -enolase and glyceraldehyde-3-phosphate dehydrogenase in virulence. Using truncation followed by peptide mapping experiments the actin and plasminogen binding sites of GBS-PGK were located to the amino acids 126-134 and amino acids 302-306. Using site directed mutagenesis, targeting these two locations within the GBS-PGK molecule, I have reduced the actin and plasminogen binding by GBS-PGK without affecting the glycolytic activity.
  In conclusion, the research presented in this thesis identifies the pathway utilized by GBS-PGK to become surface expressed, identifies potential virulence functions of surface expressed GBS-PGK and identifies mutations within the pgk gene that could prevent these virulence functions without affecting glycolysis. This work contributes to our understanding of surface expressed glycolytic enzymes and should facilitate future research determining the function of surface expressed GBS-PGK.

• Subjects / Keywords

  • Group B Streptococcus
  • Glycolytic
  • Phosphoglycerate Kinase

• Graduation date

  Spring 2012

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3J07G

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.