2b38
From Proteopedia
(New page: 200px<br /><applet load="2b38" size="450" color="white" frame="true" align="right" spinBox="true" caption="2b38" /> '''Solution structure of kalata B8'''<br /> ==...) |
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| - | [[Image:2b38.gif|left|200px]]<br /><applet load="2b38" size=" | + | [[Image:2b38.gif|left|200px]]<br /><applet load="2b38" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="2b38" /> | caption="2b38" /> | ||
'''Solution structure of kalata B8'''<br /> | '''Solution structure of kalata B8'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The cyclotides are a family of circular proteins with a range of | + | The cyclotides are a family of circular proteins with a range of biological activities and potential pharmaceutical and agricultural applications. The biosynthetic mechanism of cyclization is unknown and the discovery of novel sequences may assist in achieving this goal. In the present study, we have isolated a new cyclotide from Oldenlandia affinis, kalata B8, which appears to be a hybrid of the two major subfamilies (Mobius and bracelet) of currently known cyclotides. We have determined the three-dimensional structure of kalata B8 and observed broadening of resonances directly involved in the cystine knot motif, suggesting flexibility in this region despite it being the core structural element of the cyclotides. The cystine knot motif is widespread throughout Nature and inherently stable, making this apparent flexibility a surprising result. Furthermore, there appears to be isomerization of the peptide backbone at an Asp-Gly sequence in the region involved in the cyclization process. Interestingly, such isomerization has been previously characterized in related cyclic knottins from Momordica cochinchinensis that have no sequence similarity to kalata B8 apart from the six conserved cysteine residues and may result from a common mechanism of cyclization. Kalata B8 also provides insight into the structure-activity relationships of cyclotides as it displays anti-HIV activity but lacks haemolytic activity. The 'uncoupling' of these two activities has not previously been observed for the cyclotides and may be related to the unusual hydrophilic nature of the peptide. |
==About this Structure== | ==About this Structure== | ||
| - | 2B38 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Oldenlandia_affinis Oldenlandia affinis]. Full crystallographic information is available from [http:// | + | 2B38 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Oldenlandia_affinis Oldenlandia affinis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2B38 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Oldenlandia affinis]] | [[Category: Oldenlandia affinis]] | ||
[[Category: Protein complex]] | [[Category: Protein complex]] | ||
| - | [[Category: Clark, R | + | [[Category: Clark, R J.]] |
| - | [[Category: Craik, D | + | [[Category: Craik, D J.]] |
| - | [[Category: Daly, N | + | [[Category: Daly, N L.]] |
| - | [[Category: Plan, M | + | [[Category: Plan, M R.]] |
[[Category: beta-hairpin]] | [[Category: beta-hairpin]] | ||
[[Category: cyclic backbone]] | [[Category: cyclic backbone]] | ||
[[Category: cystine knot]] | [[Category: cystine knot]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:33:40 2008'' |
Revision as of 14:33, 21 February 2008
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Solution structure of kalata B8
Overview
The cyclotides are a family of circular proteins with a range of biological activities and potential pharmaceutical and agricultural applications. The biosynthetic mechanism of cyclization is unknown and the discovery of novel sequences may assist in achieving this goal. In the present study, we have isolated a new cyclotide from Oldenlandia affinis, kalata B8, which appears to be a hybrid of the two major subfamilies (Mobius and bracelet) of currently known cyclotides. We have determined the three-dimensional structure of kalata B8 and observed broadening of resonances directly involved in the cystine knot motif, suggesting flexibility in this region despite it being the core structural element of the cyclotides. The cystine knot motif is widespread throughout Nature and inherently stable, making this apparent flexibility a surprising result. Furthermore, there appears to be isomerization of the peptide backbone at an Asp-Gly sequence in the region involved in the cyclization process. Interestingly, such isomerization has been previously characterized in related cyclic knottins from Momordica cochinchinensis that have no sequence similarity to kalata B8 apart from the six conserved cysteine residues and may result from a common mechanism of cyclization. Kalata B8 also provides insight into the structure-activity relationships of cyclotides as it displays anti-HIV activity but lacks haemolytic activity. The 'uncoupling' of these two activities has not previously been observed for the cyclotides and may be related to the unusual hydrophilic nature of the peptide.
About this Structure
2B38 is a Protein complex structure of sequences from Oldenlandia affinis. Full crystallographic information is available from OCA.
Reference
Kalata B8, a novel antiviral circular protein, exhibits conformational flexibility in the cystine knot motif., Daly NL, Clark RJ, Plan MR, Craik DJ, Biochem J. 2006 Feb 1;393(Pt 3):619-26. PMID:16207177
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