Molecular and structural characterization of the PezAT chromosomal toxin-antitoxin system of the human pathogen Streptococcus pneumoniae.
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.
Khoo
Seok Kooi
SK
Department of Biomolecular Mechanisms, Max-Planck-Institute for Medical Research, 69120 Heidelberg, Germany.
Loll
Bernhard
B
Chan
Wai Ting
WT
Shoeman
Robert L
RL
Ngoo
Lena
L
Yeo
Chew Chieng
CC
Meinhart
Anton
A
D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005796:Genes / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D009876:Operon / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000502:physiology; D011485:Protein Binding / Q000235:genetics; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity; D013297:Streptococcus pyogenes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D040681:Structural Homology, Protein; D014158:Transcription, Genetic / Q000502:physiology; D014166:Transferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; D014166:Transferases