Defense Date

2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Microbiology & Immunology

First Advisor

Gail E. Christie

Second Advisor

Darrell L. Peterson

Third Advisor

Michael M. McVoy

Fourth Advisor

H. Tonie Wright

Fifth Advisor

Kim K. Jefferson

Sixth Advisor

Gordon L. Archer

Abstract

Ribosomal protein L27 is a component of the eubacterial large ribosomal subunit that has been shown to play a critical role in substrate stabilization during protein synthesis. This function is mediated by the L27 N-terminus, which protrudes into the peptidyl transferase center where it interacts with both A-site and P-site tRNAs as well as with 23S rRNA. We observed that L27 in S. aureus and other Firmicutes is encoded with a short N-terminal extension that is not present in most Gram-negative organisms, and is absent from mature ribosomes. The extension contains a conserved cleavage motif; nine N-terminal amino acids are post-translationally removed from L27 by a site-specific protease so that conserved residues important for tRNA stabilization at the peptidyl transferase center are exposed. We have identified a novel cysteine protease in S. aureus that performs this cleavage. This protease, which we have named Prp, is conserved in all bacteria containing the L27 N-terminal extension. L27 cleavage was shown to be essential in S. aureus; un-cleavable L27 did not complement an L27 deletion. Cleavage appears to play an essential regulatory role, as a variant of L27 lacking the cleavage motif could not complement. Ribosomal biology in eubacteria has largely been studied in E. coli; our findings indicate that there are aspects of the basic biology of the ribosome in S. aureus and other related bacteria that differ substantially from that of E. coli. This research lays the foundation for the development of new therapeutic approaches that target this novel, essential pathway.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-4-2015