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| [[Image:2p5t.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_2p5t| PDB=2p5t | SCENE= }} | | {{STRUCTURE_2p5t| PDB=2p5t | SCENE= }} |
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| '''Molecular and structural characterization of the PezAT chromosomal toxin-antitoxin system of the human pathogen Streptococcus pneumoniae'''
| | ===Molecular and structural characterization of the PezAT chromosomal toxin-antitoxin system of the human pathogen Streptococcus pneumoniae=== |
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| ==Overview==
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| The chromosomal pezT gene of the Gram-positive pathogen Streptococcus pneumoniae encodes a protein that is homologous to the zeta toxin of the Streptococcus pyogenes plasmid pSM19035-encoded epsilon-zeta toxin-antitoxin system. Overexpression of pezT in Escherichia coli led to severe growth inhibition from which the bacteria recovered approximately 3 h after induction of expression. The toxicity of PezT was counteracted by PezA, which is encoded immediately upstream of pezT and shares weak sequence similarities in the C-terminal region with the epsilon antitoxin. The pezAT genes form a bicistronic operon that is co-transcribed from a sigma(70)-like promoter upstream of pezA and is negatively autoregulated with PezA functioning as a transcriptional repressor and PezT as a co-repressor. Both PezA and the non-toxic PezA(2)PezT(2) protein complex bind to a palindrome sequence that overlaps the promoter. This differs from the epsilon-zeta system in which epsilon functions solely as the antitoxin and transcriptional regulation is carried out by another protein designated omega. Results from site-directed mutagenesis experiments demonstrated that the toxicity of PezT is dependent on a highly conserved phosphoryltransferase active site and an ATP/GTP nucleotide binding site. In the PezA(2)PezT(2) complex, PezA neutralizes the toxicity of PezT by blocking the nucleotide binding site through steric hindrance.
| | The line below this paragraph, {{ABSTRACT_PUBMED_17488720}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 17488720 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_17488720}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Phosphoryltransferase]] | | [[Category: Phosphoryltransferase]] |
| [[Category: Postsegregational killing system]] | | [[Category: Postsegregational killing system]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 12:25:45 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 03:41:50 2008'' |
