 |
PDBsum entry 1apf
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cardiac stimulant
|
PDB id
|
|
|
|
1apf
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Solution structure of the cardiostimulant polypeptide anthopleurin-B and comparison with anthopleurin-A.
|
|
|
Authors
|
|
S.A.Monks,
P.K.Pallaghy,
M.J.Scanlon,
R.S.Norton.
|
|
|
Ref.
|
|
Structure, 1995,
3,
791-803.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
BACKGROUND: The polypeptide anthopleurin-B (AP-B) is one of a number of related
toxins produced by sea anemones. AP-B delays inactivation of the voltage-gated
sodium channel of excitable tissue. In the mammalian heart, this effect is
manifest as an increase in the force of contraction. As a result, there is
interest in exploiting the anthopleurins as lead compounds in the design of
novel cardiac stimulants. Essential to this endeavour is a high-resolution
solution structure of the molecule describing the positions of functionally
important side chains. RESULTS: AP-B exists in multiple conformations in
solution as a result of cis-trans isomerization about the Gly40-Pro41 peptide
bond. The solution structure of the major conformer of AP-B has been determined
by two-dimensional 1H NMR at pH 4.5 and 25 degrees C. The core structure is a
four-stranded, antiparallel beta-sheet (residues 2-4, 20-23, 34-37 and 45-48)
and includes several beta-turns (6-9, 25-28, 30-33). Three loops connect the
beta-strands, the longest and least well defined being the first loop, extending
from residues 8-17. These features are shared by other members of this family of
sea anemone toxins. The locations of a number of side chains which are important
for the cardiac stimulatory activity of AP-B are well defined in the structures.
CONCLUSIONS: We have described the solution structure of AP-B and compared it
with that of AP-A, from which it differs by substitutions at seven amino acid
positions. It shares an essentially identical fold with AP-A yet is about
10-fold more active. Comparison of the structures, particularly in the region of
residues essential for activity, gives a clearer indication of the location and
extent of the cardioactive pharmacophore in these polypeptides.
|
|
|
|
|
|
|
|
Figure 2.
Figure 2. Summary of sequential and medium-range connectivities
for AP-B at pH 4.5 and 298 K. Filled bars indicate the
sequential connectivities, with the heights of the bars
indicating their strength. Medium-range connectivities are also
shown, but the heights of the bars do not indicate the
strength of these interactions. Hatched bars correspond to
sequential d[αδ] connectivities for prolines, except for
Gly40–Pro41 where a d[αα] connectivity was observed. A star
(*) indicates that the cross-peak could not be observed due to
peak overlap or water suppression. Values of ^3JHN-CaH >8 Hz are
indicated by ↑ while values <5.5 Hz are indicated by ↓.
Slowly exchanging amide protons (visible in at least two
consecutive TOCSY spectra recorded after dissolution in ^2H[2]O)
are indicated by filled circles and those with intermediate
exchange rates (visible in only the first TOCSY spectrum after
dissolution in ^2H[2]O) by open circles. Figure 2. Summary of
sequential and medium-range connectivities for AP-B at pH 4.5
and 298 K. Filled bars indicate the sequential connectivities,
with the heights of the bars indicating their strength.
Medium-range connectivities are also shown, but the heights of
the bars do not indicate the strength of these interactions.
Hatched bars correspond to sequential d[αδ] connectivities for
prolines, except for Gly40–Pro41 where a d[αα] connectivity
was observed. A star (*) indicates that the cross-peak could not
be observed due to peak overlap or water suppression. Values of
^3JHN-CaH >8 Hz are indicated by ↑ while values <5.5 Hz are
indicated by ↓. Slowly exchanging amide protons (visible in at
least two consecutive TOCSY spectra recorded after dissolution
in ^2H[2]O) are indicated by filled circles and those with
intermediate exchange rates (visible in only the first TOCSY
spectrum after dissolution in ^2H[2]O) by open circles.
|
|
Figure 9.
Figure 9. (a) Stereo ribbon diagrams of superpositions of the
structures of AP-B and AP-A. For each molecule, the structure
closest to the geometric average is shown. Structures were
superimposed over the backbone heavy atoms of residues 2–7 and
18–49, corresponding to the well-defined region of AP-B.
Colours are as follows: mauve/pink indicates the well-defined
region of AP-B, magenta the poorly defined loop; turquoise
indicates the well-defined region of AP-A, purple the poorly
defined loop. The side chains of Asp7, Asp9, Lys37, His39 and
Lys48 are shown in white in AP-B and red in AP-A. (b) Stereoview
of the structure of AP-B closest to the geometric average and
showing the positions of some of the residues (Asp7, Asp9,
Arg12, Asn35, Lys37, His39 and Lys48 coloured magenta) thought
to contribute to the receptor-binding surface of the molecule
(see text). A Connolly surface generated with a probe radius of
1.4 å is shown; the orientation of the molecule is the
same as in Figure 5. Figure 9. (a) Stereo ribbon diagrams of
superpositions of the structures of AP-B and AP-A. For each
molecule, the structure closest to the geometric average is
shown. Structures were superimposed over the backbone heavy
atoms of residues 2–7 and 18–49, corresponding to the
well-defined region of AP-B. Colours are as follows: mauve/pink
indicates the well-defined region of AP-B, magenta the poorly
defined loop; turquoise indicates the well-defined region of
AP-A, purple the poorly defined loop. The side chains of Asp7,
Asp9, Lys37, His39 and Lys48 are shown in white in AP-B and red
in AP-A. (b) Stereoview of the structure of AP-B closest to the
geometric average and showing the positions of some of the
residues (Asp7, Asp9, Arg12, Asn35, Lys37, His39 and Lys48
coloured magenta) thought to contribute to the receptor-binding
surface of the molecule (see text). A Connolly surface generated
with a probe radius of 1.4 å is shown; the orientation of
the molecule is the same as in [4]Figure 5.
|
|
|
|
|
|
The above figures are
reprinted
by permission from Cell Press:
Structure
(1995,
3,
791-803)
copyright 1995.
|
|
|
Secondary reference #1
|
|
|
Title
|
|
Three-Dimensional structure in solution of the polypeptide cardiac stimulant anthopleurin-A.
|
|
|
Authors
|
|
P.K.Pallaghy,
M.J.Scanlon,
S.A.Monks,
R.S.Norton.
|
|
|
Ref.
|
|
Biochemistry, 1995,
34,
3782-3794.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
Secondary reference #2
|
|
|
Title
|
|
Structure and structure-Function relationships of sea anemone proteins that interact with the sodium channel.
|
|
|
Author
|
|
R.S.Norton.
|
|
|
Ref.
|
|
Toxicon, 1991,
29,
1051-1084.
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
Secondary reference #3
|
|
|
Title
|
|
Sea anemone toxins: structure and action
|
|
|
Author
|
|
W.R.Kem.
|
|
|
Ref.
|
|
the biology of nematocysts ...
|
|
|
|
|
|
|
|
