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The Enterococcus faecalis cytolysin:...

Coburn, Phillip Stephen.

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The Enterococcus faecalis cytolysin: Analysis of structure/function relationships and elucidation of a novel means of gene regulation in response to the detection of target cells.

Record Type:	Electronic resources : Monograph/item
Title/Author:	The Enterococcus faecalis cytolysin: Analysis of structure/function relationships and elucidation of a novel means of gene regulation in response to the detection of target cells./
Author:	Coburn, Phillip Stephen.
Description:	187 p.
Notes:	Source: Dissertation Abstracts International, Volume: 65-11, Section: B, page: 5533.
Contained By:	Dissertation Abstracts International65-11B.
Subject:	Biology, Microbiology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3154438
ISBN:	0496149962

The Enterococcus faecalis cytolysin: Analysis of structure/function relationships and elucidation of a novel means of gene regulation in response to the detection of target cells.
Coburn, Phillip Stephen.

The Enterococcus faecalis cytolysin: Analysis of structure/function relationships and elucidation of a novel means of gene regulation in response to the detection of target cells. - 187 p.

Source: Dissertation Abstracts International, Volume: 65-11, Section: B, page: 5533.

Thesis (Ph.D.)--The University of Oklahoma Health Sciences Center, 2004.

The enterococcal cytolysin is a unique, two-peptide lytic toxin that has evolved multiple activities in a single system. This novel bacterial peptide system possesses lytic activity against both prokaryotic and eukaryotic cells. Moreover, the smaller of the two peptides, CylL S″, functions to activate expression of the cytolysin gene cluster by a quorum-sensing, autoinduction mechanism. The cytolysin has been demonstrated to impact the course and outcome of disease in animal models of enterococcal infection, and enrichment among clinical isolates has suggested a role for the cytolysin in human infection. Thus, the cytolysin represents a potential target for new therapeutics designed to attenuate enterococcal infection. In the current study, a novel producer self-protection determinant at the 3' end of the cytolysin operon was described. Deletion analysis and specific mutagenesis isolated this producer immunity function to a single open reading frame, and demonstrated that producer immunity is unrelated to cytolysin activation. The role of the larger of the two peptides, CylLL″, in the regulation of cytolysin expression was evaluated and it was demonstrated that in the absence of target cells, CylLL″ formed complexes with CylLS ″, preventing the latter from triggering high level cytolysin expression. In the presence of target cells, however, CylLL ″ bound preferentially to the target, allowing free CylL S″ to accumulate above the induction threshold. Thus, CylLL″ provides enterococci with a mechanism for sounding the environment for the presence of target cells, and in response, for expressing high levels of cytolysin to affect target cell lysis. Finally, structure/activity relationships of the CylLS″ subunit were examined by alanine scanning mutagenesis. No amino acid within the mature sequence of CylLS″ was dispensable for all activities. However, the results demonstrated that hemolytic, antibacterial, and signaling activities are separable activities, and indicate that CylL S″ is precisionally honed to maintain a balance between activity against eukaryotic cells and suicidal production due to increased bacteriocin activity, and/or indirectly due to increased production from greater signaling capacity.

ISBN: 0496149962Subjects--Topical Terms:

1017734
Biology, Microbiology.

The Enterococcus faecalis cytolysin: Analysis of structure/function relationships and elucidation of a novel means of gene regulation in response to the detection of target cells.
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245 1 4 $a The Enterococcus faecalis cytolysin: Analysis of structure/function relationships and elucidation of a novel means of gene regulation in response to the detection of target cells.
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520 $a The enterococcal cytolysin is a unique, two-peptide lytic toxin that has evolved multiple activities in a single system. This novel bacterial peptide system possesses lytic activity against both prokaryotic and eukaryotic cells. Moreover, the smaller of the two peptides, CylL S″, functions to activate expression of the cytolysin gene cluster by a quorum-sensing, autoinduction mechanism. The cytolysin has been demonstrated to impact the course and outcome of disease in animal models of enterococcal infection, and enrichment among clinical isolates has suggested a role for the cytolysin in human infection. Thus, the cytolysin represents a potential target for new therapeutics designed to attenuate enterococcal infection. In the current study, a novel producer self-protection determinant at the 3' end of the cytolysin operon was described. Deletion analysis and specific mutagenesis isolated this producer immunity function to a single open reading frame, and demonstrated that producer immunity is unrelated to cytolysin activation. The role of the larger of the two peptides, CylLL″, in the regulation of cytolysin expression was evaluated and it was demonstrated that in the absence of target cells, CylLL″ formed complexes with CylLS ″, preventing the latter from triggering high level cytolysin expression. In the presence of target cells, however, CylLL ″ bound preferentially to the target, allowing free CylL S″ to accumulate above the induction threshold. Thus, CylLL″ provides enterococci with a mechanism for sounding the environment for the presence of target cells, and in response, for expressing high levels of cytolysin to affect target cell lysis. Finally, structure/activity relationships of the CylLS″ subunit were examined by alanine scanning mutagenesis. No amino acid within the mature sequence of CylLS″ was dispensable for all activities. However, the results demonstrated that hemolytic, antibacterial, and signaling activities are separable activities, and indicate that CylL S″ is precisionally honed to maintain a balance between activity against eukaryotic cells and suicidal production due to increased bacteriocin activity, and/or indirectly due to increased production from greater signaling capacity.
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