 |
PDBsum entry 1e2a
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
The structure of enzyme iialactose from lactococcus lactis reveals a new fold and points to possible interactions of a multicomponent system.
|
|
|
Authors
|
|
P.Sliz,
R.Engelmann,
W.Hengstenberg,
E.F.Pai.
|
|
|
Ref.
|
|
Structure, 1997,
5,
775-788.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
BACKGROUND: The bacterial phosphoenolpyruvate: sugar phosphotransferase system
(PTS) is responsible for the binding, transmembrane transport and
phosphorylation of numerous sugar substrates. The system is also involved in the
regulation of a variety of metabolic and transcriptional processes. The PTS
consists of two non-specific energy coupling components, enzyme I and a heat
stable phosphocarrier protein (HPr), as well as several sugar-specific
multiprotein permeases known as enzymes II. In most cases, enzymes IIA and IIB
are located in the cytoplasm, while enzyme IIC acts as a membrane channel.
Enzyme IIAlactose belongs to the lactose/cellobiose-specific family of enzymes
II, one of four functionally and structurally distinct groups. The protein,
which normally functions as a trimer, is believed to separate into its subunits
after phosphorylation. RESULTS: The crystal structure of the trimeric enzyme
IIAlactose from Lactococcus lactis has been determined at 2.3 A resolution. The
subunits of the enzyme, related to each other by the inherent threefold
rotational symmetry, possess interesting structural features such as
coiled-coil-like packing and a methionine cluster. The subunits each comprise
three helices (I, II and III) and pack against each other forming a nine-helix
bundle. This helical bundle is stabilized by a centrally located metal ion and
also encloses a hydrophobic cavity. The three phosphorylation sites (His78 on
each monomer) are located in helices III and their sidechains protrude into a
large groove between helices I and II of the neighbouring subunits. A model of
the complex between phosphorylated HPr and enzyme IIAlactose has been
constructed. CONCLUSIONS: Enzyme IIAlactose is the first representative of the
family of lactose/cellobiose-specific enzymes IIA for which a three-dimensional
structure has been determined. Some of its structural features, like the
presence of two histidine residues at the active site, seem to be common to all
enzymes no overall structural homology is observed to any PTS proteins or to any
other proteins in the Protein Data Bank. Enzyme IIAlactose shows surface
complementarity to the phosphorylated form of HPr and several energetically
favourable interactions between the two molecules can be predicted.
|
|
|
|
|
|
Figure 8.
Figure 8. Stereo view representation of a modelled enzyme
IIA-HPr complex. With knowledge of the phosphorylation site, the
family of NMR structures of P-HPr (PDB code 1PFH coloured in
red) was docked into the crystallographic model of enzyme IIA.
The P-HPr ensemble of structures was rotated around the apical
axis (red line) to minimize clashes and short contacts between
the two proteins. Residues possibly involved in electrostatic
interaction are Glu64[IIA] and Arg17[HPr]. Sidechains of
His78[IIA], His82[IIA] and P-His15[HPr] are displayed and
coloured by atom type.
|
|
|
|
|
|
The above figure is
reprinted
by permission from Cell Press:
Structure
(1997,
5,
775-788)
copyright 1997.
|
|
|
Secondary reference #1
|
|
|
Title
|
|
Crystallization and preliminary structural studies of lactose-Specific enzyme iia from lactococcus lactis.
|
|
|
Authors
|
|
P.Sliz,
K.H.Schörter,
W.M.De vos,
E.F.Pai.
|
|
|
Ref.
|
|
Acta Crystallogr D Biol Crystallogr, 1996,
52,
1199-1201.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Figure 2.
Fig. 2. (a) A typical 1
° oscillation image for a crystal of lactose-specific
enzyme IIA from
L. lactis.
The image was recorded on an 18 cm
diameter MAR image plate on beamline X31 of the EMBL outstation
of DESY, Hamburg, Germany. With a crystal-to-film distance of
200 mm, 2 = 0.94 A and a ring current of 99 mA, the typical exposure
time was 3 rain. (b) Enlargement of the edge of the diffraction image
showing reflections at high resolution (up to 2.3 .A
0.
|
|
Figure 4.
Fig. 4. uv}~ section of the isomorphous Patterson difference map
produced with
PIIASES (Furey,
1991 ). Contours are drawn at levels
of lo- starting at 30-. The peak a which is observed at
u
= 0.223,
v = 0.145 and w= 0.249 has a height of 140-, which represents 8.3%
of the height of the origin peak. All other peaks are related to peak a
by crystallographic symmetry and correspond to a single binding site
of trimethyl lead aceate.
|
|
|
|
|
|
The above figures are
reproduced from the cited reference
with permission from the IUCr
|
|
|
|
|
|
|
