Insecticidal delta-endotoxin Cyt2Ba from Bacillus thuringiensis: Difference between revisions

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Eran Hodis, Alexander Berchansky, Joel L. Sussman, Eric Martz, Jaime Prilusky, Michal Harel, David Canner

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+<StructureSection load='' size='350' side='right' scene='Cyt2Ba/Cartoon_spectrum/2' caption=''>
 [[Image:Cyt_trim.jpg|left|150px]]
-{{STRUCTURE_2rci|  PDB=2rci  |  SCENE=Cyt2Ba/Cartoon_spectrum/2  }}
 ===High-resolution crystal structure of activated Cyt2Ba monomer (δ-endotoxin) from ''Bacillus thuringiensis'' subsp. ''israelensis''===
 {{ABSTRACT_PUBMED_18571667}}
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-<applet load='Cyt2Baa.pdb' size='500' frame='true' align='left' caption=Cyt2Ba' />
+The [http://en.wikipedia.org/wiki/Crystal_structure crystal structure] of the [http://en.wikipedia.org/wiki/Proteolysis proteolytically] activated monomeric form of Cyt2Ba was determined at 1.8Å resolution. It consists of a single domain of  <scene name='Cyt2Ba/Alpha_beta/5'>α/β</scene> architecture with a <scene name='Cyt2Ba/Beta/2'>β-sheet</scene> (yellow) surrounded by 2 <scene name='Cyt2Ba/Alpha/2'>α-helical</scene> layers <font color='red'><b>(red)</b></font> forming a cytolysin fold. The [http://en.wikipedia.org/wiki/Beta_sheet β-sheet] is comprised of 6 anti-parallel β-strands (β1-β6). On one side of this sheet there is an [http://en.wikipedia.org/wiki/Alpha_helix α-helix] layer consisting of α1, α2; and on the other side  a second α-helix layer, composed of α3-α5. The β-strands β2-β5 of the central β-sheet have a modified Greek-key topology. The Greek key motif consists of four adjacent antiparallel strands and their linking loops. It consists of three antiparallel strands connected by hairpins, while the fourth is adjacent to the first and linked to the third by a longer loop [http://en.wikipedia.org/wiki/Beta_sheet]. <font color='gray'><b>Cyt2Ba (gray)</b></font> has only 16% sequence identity with <font color='red'><b>VVA2 (colored red,</b></font> [[1pp0]]), however they both have a cytolysin fold and their overall structure is very similar (see their <scene name='Cyt2Ba/Cyt2ba_vva/3'>structural alignment</scene>).
+A remarkable similarity is observed between the structures of the endogenously cleaved Cyt2Ba <scene name='Cyt2Ba/Cyt2ba_monomer/2'>monomer</scene> <font color='gray'><b>(gray)</b></font> and the <scene name='Cyt2Ba/Alignment/2'>corresponding region</scene> <font color='red'><b>(red)</b></font> within the inactive protoxin  <scene name='Cyt2Ba/Dimer/2'>dimer</scene> of Cyt2Aa ([[1cby]], monomers <font color='red'><b>A</b></font> and <font color='blue'><b>B</b></font> of Cyt2Aa shown <font color='red'><b>red</b></font> and <font color='blue'><b>blue</b></font>, respectively, the N- and C-termini are shown in spacefilling representation). Although, [[1cby]] is a 1 chain structure, the biological relevant molecule for [[1cby]] can be assembled from the contents of the deposited coordinates by the application of crystallographic symmetry operations to give a dimer. It can be [http://www.ebi.ac.uk/pdbe/pqs/macmol/1cby.mmol downloaded]. Each monomer of Cyt2Aa ([[1cby]]), consists of an additional β-strand at its N-terminus and an additional α-helix at its C-terminus compared to the cleaved Cyt2Ba. The <scene name='Cyt2Ba/Dimer_mesh/12'>dimer interface</scene> of Cyt2Aa is held together by the intertwined N-terminal strands from both monomers. The cleavage of Cyt2Aa <scene name='Cyt2Ba/Dimer_mes/1'>removes</scene> the N- and C-terminal segments, prevents dimer formation and releases an <scene name='Cyt2Ba/Monomer_toxin/4'> active toxin monomer</scene>. Similarly, in Cyt2Ba the proteolysis causes the removal of 34 amino acids at its N-terminus and 28 or 30 residues at its C-terminus forming the crystallized toxic monomer.
-The crystal structure of the proteolytically activated monomeric form of Cyt2Ba was determined at 1.8Å resolution. It consists of a single domain of  <scene name='Cyt2Ba/Alpha_beta/5'>α/β</scene> architecture with a <scene name='Cyt2Ba/Beta/2'>β-sheet</scene> <font color='yellow'><b>(yellow)</b></font> surrounded by 2 <scene name='Cyt2Ba/Alpha/2'>α-helical</scene> layers <font color='red'><b>(red)</b></font> forming a cytolysin fold. The β-sheet comprises 6 anti-parallel β-strands (β1-β6), on one side of this sheet there is an α-helix layer consisting of α1, α2; and on the other side  a second α-helix layer, composed of α3-α5, is located. The β-strands β2-β5 of the central β-sheet have a modified Greek-key topology.
+{{Clear}}
+==Conclusions==
+The crystal structure of monomeric Cyt2Ba is the first structure of a [http://en.wikipedia.org/wiki/Toxicity toxic] form of the Cyt family. Its structure is [http://en.wikipedia.org/wiki/Homology_(biology) homologous] to the corresponding region of Cyt2Aa and to that of VVA2. This structural comparison shows that the toxicity of Cyt2Ba, Cyt2Aa and VVA2 is an inherent property of the monomer and not the result of secondary structure rearrangement upon cleavage. Solving the 3D structure of these proteins extends the knowledge of the cytolytic machinery of pore-forming toxins and helps in designing novel membrane-active cytotoxins.
+</StructureSection>
+__NOTOC__
+==3D structures of δ-endotoxin==
-Cyt2Ba has only 16% sequence identity with VVA2 ([[1pp0]]), however they both have a cytolysin fold and their overall structure is very similar (see their <scene name='Cyt2Ba/Cyt2ba_vva/3'>structural alignment</scene>).
+[[Delta-endotoxin]]
-A remarkable similarity is observed between the structures of the endogenously cleaved Cyt2Ba <scene name='Cyt2Ba/Cyt2ba_monomer/2'>monomer</scene> (gray) and the <scene name='Cyt2Ba/Alignment/2'>corresponding region</scene> within the inactive protoxin  <scene name='Cyt2Ba/Dimer/2'>dimer</scene> of Cyt2Aa (monomers A and B of Cyt2Aa shown red and blue, respectively, the N- and C-termini are shown in spacefill representation). Each monomer of Cyt2Aa ([[1cby]]), consists of an additional β-strand at its N-terminus and α-helix at its C-terminus compared to the cleaved Cyt2Ba. The <scene name='Cyt2Ba/Dimer_mesh/12'>dimer interface</scene> of Cyt2Aa is held together by the intertwined N-terminal strands from both monomers. The cleavage of Cyt2Aa <scene name='Cyt2Ba/Dimer_mes/1'>removes</scene> the N and C termini segments, prevents dimer formation and releases a <scene name='Cyt2Ba/Monomer_toxin/4'>monomer active toxin</scene>. Similarly, in Cyt2Ba the proteolysis causes the removal of 34 amino acids at its N-terminal and 28 or 30 residues at its C-terminus forming the crystallized toxic monomer.
-{{Clear}}
-==Conclusions==
-The crystal structure of monomeric Cyt2Ba is the first structure of a toxic form of the Cyt family. Its structure is homologous to the corresponding region of Cyt2Aa and to that of VVA2. This structural comparison shows that the toxicity of Cyt2Ba, Cyt2Aa and VVA2 is an inherent property of the monomer and not the result of secondary structure rearrangement upon cleavage. A comprehensive understanding of the toxic activities of these proteins may not only extend our understanding as to the cytolytic machinery of pore forming toxins but also help to design novel membrane-active cytotoxins.
+==Additional Resources==
+For additional information, see: [[Toxins]]
+<br />
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