 |
PDBsum entry 2h1c
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Gene regulation
|
PDB id
|
|
|
|
2h1c
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Structure of fitab from neisseria gonorrhoeae bound to DNA reveals a tetramer of toxin-Antitoxin heterodimers containing pin domains and ribbon-Helix-Helix motifs.
|
|
|
Authors
|
|
K.Mattison,
J.S.Wilbur,
M.So,
R.G.Brennan.
|
|
|
Ref.
|
|
J Biol Chem, 2006,
281,
37942-37951.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
Abstract
|
|
|
Neisseria gonorrhoeae is a sexually transmitted pathogen that initiates
infections in humans by adhering to the mucosal epithelium of the urogenital
tract. The bacterium then enters the apical region of the cell and traffics
across the cell to exit into the subepithelial matrix. Mutations in the fast
intracellular trafficking (fitAB) locus cause the bacteria to transit a
polarized epithelial monolayer more quickly than the wild-type parent and to
replicate within cells at an accelerated rate. Here, we describe the crystal
structure of the toxin-antitoxin heterodimer, FitAB, bound to a high affinity
36-bp DNA fragment from the fitAB promoter. FitA, the antitoxin, binds DNA
through its ribbon-helix-helix motif and is tethered to FitB, the toxin, to form
a heterodimer by the insertion of a four turn alpha-helix into an extensive FitB
hydrophobic pocket. FitB is composed of a PIN (PilT N terminus) domain, with a
central, twisted, 5-stranded parallel beta-sheet that is open on one side and
flanked by five alpha-helices. FitB in the context of the FitAB complex does not
display nuclease activity against tested PIN substrates. The FitAB complex
points to the mechanism by which antitoxins with RHH motifs can block the
activity of toxins with PIN domains. Interactions between two FitB molecules
result in the formation of a tetramer of FitAB heterodimers, which binds to the
36-bp DNA fragment and provides an explanation for how FitB enhances the DNA
binding affinity of FitA.
|
|
|
|
|
|
|
|
Figure 2.
FIGURE 2. Ribbon diagram of the structure of the FitAB-IR36
complex. a, the FitA and FitB proteins are colored magenta and
cyan, respectively. DNA is colored according to gray (carbon),
red (oxygen), blue (nitrogen), and yellow (phosphorus). The four
FitAB heterodimers are numbered from I to IV. b, view of a
rotated to demonstrate that the two FitA  sheets bind on the same
face of the DNA helix. c, sequence of the 36-bp IR36 site used
for crystallization. The 8-bp inverted repeat half-sites are
highlighted in yellow.
|
|
Figure 4.
FIGURE 4. FitA-DNA contacts. a, schematic diagram of the
FitA-DNA contacts. The deoxyriboses of each nucleotide are
numbered, labeled, and shown as pentagons. Side chain DNA
hydrogen bonds are indicated by blue arrows, backbone amide-DNA
hydrogen bonds are green arrows, and van der Waals contacts are
shown as yellow arrows. Each FitA residue is from subunit I, II,
III, or IV, as defined in the legend to Fig. 2. b, stereo view
of the composite omit electron density map of one FitA-DNA
interface contoured at 1.0  to 3.0 Å
resolution (green mesh). The FitA protein is shown as magenta
balls and sticks and the DNA is shown as balls and sticks where
gray (carbon), red (oxygen), blue (nitrogen), yellow
(phosphorus). Note the water (Wat1)-mediated contact between
Asn^8 and Thy^32'.
|
|
|
|
|
|
The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2006,
281,
37942-37951)
copyright 2006.
|
|
|
|
|
|
|
