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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-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.
+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. <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>).
-<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 (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 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-terminal 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-terminus and 28 or 30 residues at its C-terminus forming the crystallized toxic monomer.