PDBsum entry 1apf

Cardiac stimulant

PDB id: 1apf

Contents

Protein chain

49 a.a. *

* Residue conservation analysis

PDB id:

1apf

Name:

Cardiac stimulant

Title:

Anthopleurin-b, nmr, 20 structures

Structure:

Anthopleurin-b. Chain: a. Synonym: ap-b, axii

Source:

Anthopleura xanthogrammica. Giant green sea anemone. Organism_taxid: 6112. Organ: whole animal

NMR struc:

20 models

Authors:

S.A.Monks,P.K.Pallaghy,M.J.Scanlon,R.S.Norton

Key ref:

S.A.Monks et al. (1995). Solution structure of the cardiostimulant polypeptide anthopleurin-B and comparison with anthopleurin-A. Structure, 3, 791-803. PubMed id: 7582896 DOI: 10.1016/S0969-2126(01)00214-3

Date:

30-May-95 Release date: 11-Jul-96

Protein chain

P01531  (NA1B_ANTXA) -  Delta-actitoxin-Axm1b from Anthopleura xanthogrammica

Seq: 49 a.a.

Struc: 49 a.a.

DOI no: 10.1016/S0969-2126(01)00214-3

Structure 3:791-803 (1995)

PubMed id: 7582896

Solution structure of the cardiostimulant polypeptide anthopleurin-B and comparison with anthopleurin-A.

S.A.Monks, P.K.Pallaghy, M.J.Scanlon, R.S.Norton.

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.

Selected figure(s)

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.

Figures were selected by an automated process.