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[log in to unmask]" type="cite">Thesis Defense Announcement
To:  The George Mason University Community

Candidate: Nicholas Leverone
Program: Master of Science in Biology

Date:   Tuesday April 9, 2013
Time:   9:30 a.m.
Place:  George Mason University, 
	    Prince William Campus
	    Discovery Hall, Room 153

Title: "Small Peptide Derived from Human MMP12 CTD Is Antibacterial against Gram-negative and Gram-positive Pathogens,
	 Including Multi-drug Resistant S. aureus (MRSA)"

Thesis Director: Dr. Monique van Hoek

Thesis Committee:  Dr. Serguei Popov, Dr. Barney Bishop
A copy of the thesis will be available in the Johnson Center Library.  All are invited to attend the defense.

Matrix Metalloproteinase 12 (MMP12) is a macrophage produced proteolytic enzyme also known as macrophage elastase. The proteinase activity is located at its N-terminal. The C-terminal of the protein is cleaved during processing, releasing the Hemopexin-like Carboxy-terminal domain (CTD) [1-3]. The biological function of the CTD is not known. Previous work by our group demonstrated that murine MMP12 had bactericidal activity in a small peptide contained within the middle third of the CTD [4]. The goal of this study was to examine human MMP12 to determine if similar CTD-antibacterial activity could be identified. We investigated the antimicrobial properties of human MMP12 CTD with the goal of identifying potential antimicrobial peptides within this hemopexin-like protein. We tested the full-length human CTD domain for antimicrobial activity against S. aureus and other bacteria. We used three-dimensional structure analysis, comparison of known human peptides identified in blood, and bioinformatic analysis of sequences using peptide databases in order to identify strong candidates for antimicrobial activity. These candidate peptides were then synthesized and tested for antimicrobial peptide activity against S. aureus. Active peptides from this screen were further tested against other organisms, for biofilm inhibition, and for their effect on bacterial membrane integrity. The human CTD of MMP12 is antibacterial against S. aureus, P. aeruginosa, E. coli, and A. baumannii. We tested small peptides derived from CTD for antibacterial activity. Five active peptides were identified. One peptide, KY-27, displayed the lowest half-maximal effective concentration (EC50), 27.8 µM against S. aureus, and 47.45 µM against MRSA. This peptide was antimicrobial against both Gram-positive and Gram-negative bacteria, but did not inhibit biofilm formation by these organisms. When tested in an in vivo model, this peptide was able to increase survival in G. mellonella when challenged with P. aeruginosa. Our studies demonstrate that the human MMP12 CTD is antibacterial against S. aureus. We also identified a small 27 AA peptide of the CTD, KY-27, which has strong antimicrobial activity against S. aureus and multiple other pathogenic bacteria. These results suggest that KY-27 may be a vital component of the CTD bactericidal effects.