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Open Access Highly Accessed Research article

A novel bacteriophage Tail-Associated Muralytic Enzyme (TAME) from Phage K and its development into a potent antistaphylococcal protein

Vivek Daniel Paul12, Sanjeev Saravanan Rajagopalan1, Sudarson Sundarrajan1, Shilpa E George1, Jiya Y Asrani1, Renjith Pillai13, Ravisha Chikkamadaiah1, Murali Durgaiah1, Bharathi Sriram1* and Sriram Padmanabhan14

Author Affiliations

1 Gangagen Biotechnologies Pvt Ltd., No. 12, 5th Cross, Raghavendra Layout, Tumkur Road, Yeshwantpur, Bangalore 560 022, India

2 Department of Molecular Genetics, University of Toronto,1 King's College Circle, Toronto, ON-M5S 1A8, Canada

3 Lab Technologist, Pulmonary research, 559, Heritage Medical Research Center Dept of Medicine,112 St and 87 Ave, Edmonton, Alberta-T6G2S2, Canada

4 Lupin Limited, Biotechnology R & D, Gat #1156, Ghotawade Village, Mulshi Taluka, Pune-411042, India

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BMC Microbiology 2011, 11:226  doi:10.1186/1471-2180-11-226

Published: 11 October 2011

Abstract

Background

Staphylococcus aureus is a major cause of nosocomial and community-acquired infections. However, the rapid emergence of antibiotic resistance limits the choice of therapeutic options for treating infections caused by this organism. Muralytic enzymes from bacteriophages have recently gained attention for their potential as antibacterial agents against antibiotic-resistant gram-positive organisms. Phage K is a polyvalent virulent phage of the Myoviridae family that is active against many Staphylococcus species.

Results

We identified a phage K gene, designated orf56, as encoding the phage tail-associated muralytic enzyme (TAME). The gene product (ORF56) contains a C-terminal domain corresponding to cysteine, histidine-dependent amidohydrolase/peptidase (CHAP), which demonstrated muralytic activity on a staphylococcal cell wall substrate and was lethal to S. aureus cells. We constructed N-terminal truncated forms of ORF56 and arrived at a 16-kDa protein (Lys16) that retained antistaphylococcal activity. We then generated a chimeric gene construct encoding Lys16 and a staphylococcal cell wall-binding SH3b domain. This chimeric protein (P128) showed potent antistaphylococcal activity on global clinical isolates of S. aureus including methicillin-resistant strains. In addition, P128 was effective in decolonizing rat nares of S. aureus USA300 in an experimental model.

Conclusions

We identified a phage K gene that encodes a protein associated with the phage tail structure. The muralytic activity of the phage K TAME was localized to the C-terminal CHAP domain. This potent antistaphylococcal TAME was combined with an efficient Staphylococcus-specific cell-wall targeting domain SH3b, resulting in the chimeric protein P128. This protein shows bactericidal activity against globally prevalent antibiotic resistant clinical isolates of S. aureus and against the genus Staphylococcus in general. In vivo, P128 was efficacious against methicillin-resistant S. aureus in a rat nasal colonization model.