Defense Date

3-27-2009

Graduation Date

Spring 2009

Availability

Immediate Access

Submission Type

thesis

Degree Name

MS

Department

Biological Sciences

Committee Chair

Peter A. Castric

Committee Member

Jana Patton-Vogt

Committee Member

Joseph R. McCormick

Keywords

substrate specificity, PilO, peptide extension, Pseudomonas aeruginosa, O-linked glycosylation, vaccine design

Abstract

P. aeruginosa 1244 (PA1244) possesses an O-linked glycosylation system by which the glycosyltransferase, PilO, transfers a single preassembled O-antigen repeating unit to the C-terminal serine residue of pilin as a posttranslational modification. Previous work has shown that the group II pilin of PA103 can be engineered for glycosylation by extending a C-terminal serine away from the surface with a short stretch of alanine residues (Horzempa et al., 2006a). As an extension of that study, several normally non-glycosylated proteins [PA683 pilin, PA1244 PilA-E. coli (EC) alkaline phosphatase (PhoA) fusion, and EC PhoA] were engineered with C-terminal amino acid extensions and assessed for glycosylation by PilO-mediated glycan modification. Migration patterns on SDS-PAGE and an electrofocusing gel revealed that the TfpY accessory protein does not directly confer a posttranslational modification to group III PA683 pilin. The addition of two C-terminal peptide extensions, an –AAS tripeptide and a 15 amino acid PA1244 derived-peptide tail, to PA683 pilin allowed glycosylation in an LPS polymerization mutant, PA103 wzyPaO11::aacC1, when complemented with PilO. A PA1244 PilA-EC PhoA fusion and EC PhoA engineered with the C-terminal –AAS tripeptide extension were unable to be glycosylated in strain 1244 or PA103 wzyPaO11::aacC1 complemented with PilO. These results suggest the necessity of pilin-specific structures, or the necessity of a membrane anchor for enhancement of PilO substrate recognition. Additionally, larger peptide tail extensions should be considered for testing in future work. Overall, these findings provide further information on glycosylation substrate specificity and suggest the ability to glycosylate normally non-glycosylated proteins in an effort to produce potential conjugate vaccine components.

Format

PDF

Language

English

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