PDBsum entry 2p5t

Transcription regulator

PDB id: 2p5t

Contents

Protein chains

33 a.a.

92 a.a. *

244 a.a. *

* Residue conservation analysis

PDB id:

2p5t

Name:

Transcription regulator

Title:

Molecular and structural characterization of the pezat chromosomal toxin-antitoxin system of the human pathogen streptococcus pneumoniae

Structure:

Fragment of peza helix-turn-helix motif. Chain: x. Engineered: yes. Putative transcriptional regulator peza. Chain: a, c, e, g. Engineered: yes. Pezt. Chain: b, d, f, h. Engineered: yes

Source:

Streptococcus pneumoniae. Organism_taxid: 1313. Expressed in: escherichia coli. Expression_system_taxid: 562. Organism_taxid: 170187. Strain: tigr4.

Resolution:

3.20Å R-factor: 0.217 R-free: 0.277

Authors:

B.Loll,A.Meinhart

Key ref:

S.K.Khoo et al. (2007). Molecular and structural characterization of the PezAT chromosomal toxin-antitoxin system of the human pathogen Streptococcus pneumoniae. J Biol Chem, 282, 19606-19618. PubMed id: 17488720 DOI: 10.1074/jbc.M701703200

Date:

16-Mar-07 Release date: 15-May-07

Protein chain

No UniProt id for this chain

Struc: 33 a.a.

Protein chains

Q97QZ2  (PEZA_STRPN) -  Antitoxin PezA from Streptococcus pneumoniae serotype 4 (strain ATCC BAA-334 / TIGR4)

Seq: 158 a.a.

Struc: 92 a.a.

Protein chains

Q97QZ1  (PEZT_STRPN) -  Toxin PezT from Streptococcus pneumoniae serotype 4 (strain ATCC BAA-334 / TIGR4)

Seq: 253 a.a.

Struc: 244 a.a.*

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

Enzyme reactions

• Enzyme class 2: Chains A, C, E, G: E.C.?
• Enzyme class 3: Chains B, D, F, H: E.C.2.7.1.176 - UDP-N-acetylglucosamine kinase.
• Reaction: UDP-N-acetyl-alpha-D-glucosamine + ATP = UDP-N-acetyl-alpha-D-glucosamine 3'-phosphate + ADP + H⁺

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

Added reference

DOI no: 10.1074/jbc.M701703200

J Biol Chem 282:19606-19618 (2007)

PubMed id: 17488720

Molecular and structural characterization of the PezAT chromosomal toxin-antitoxin system of the human pathogen Streptococcus pneumoniae.

S.K.Khoo, B.Loll, W.T.Chan, R.L.Shoeman, L.Ngoo, C.C.Yeo, A.Meinhart.

ABSTRACT

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.

Selected figure(s)

Figure 1.
FIGURE 1. A, sequence alignment of the C-terminal domain of PezA and PezT with the epsilon/zeta system. Identical residues are colored green, highly homologous residues orange, and homologous residues yellow, respectively. Secondary structures are shown above the sequence alignment with -helices illustrated as cylinders and -strands as arrows. The region in PezT that could not be modeled into the electron density is indicated by a green line. Residues that are involved in PezA-PezA interaction are labeled with filled squares beneath the sequence alignment, and those that are involved in PezA-PezT interaction with filled triangles. Open circles label residues of PezA that inhibit the toxin PezT. Asterisks indicate those residues that were changed by site-directed mutagenesis in PezT and were shown to abolish PezT toxicity. Filled diamonds above the sequence alignment indicate residues of different PezT variants where mutations to homologous residues were observed, open diamonds mark mutations of a non-conservative nature. B, ribbon representation of the heterotetrameric PezA/PezT arrangement. Helices of PezA are colored in blue and helices of PezT in beige, respectively. -Strands in PezT are colored in red. C, surface representation of the complex colored according to the color scheme of A.

Figure 6.
FIGURE 6. A, surface representation of PezT alone, colored according to Fig. 1A. Residues that are identical with zeta and showed to impair PezT toxicity are colored in blue. An ATP molecule colored in magenta was modeled according to the position found in the chloramphenicol-phosphotransferase (29). B, effect of PezT mutations on the growth of E. coli BL21(DE3)/pLysS carrying recombinant pET11a plasmids as determined by A[600] and log CFU. Growth profile of wild-type PezT is shown as (x) for A[600] values (on top) and black bars in log CFU (bottom). Growth profiles of the following mutants following IPTG induction are shown: T117V ( ; green bars), T120V ( ; blue bars), and K45A ( ; yellow bars). The R157A, R170A, and D66T mutations yielded nontoxic growth profiles similar to those of K45A and T117V and are not presented in the figure.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2007, 282, 19606-19618) copyright 2007.

Figures were selected by the author.