2b38

Solution structure of kalata B8

spinqualitylabelsall models 2b38 Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2b38 is a 1 chain structure with sequence from Oldenlandia affinis. Full experimental information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Solution NMR, 20 models Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function KAB8_OLDAF Probably participates in a plant defense mechanism. Inhibits the cytopathic effects of the human immunodeficiency virus. Has no hemolytic activity. Publication Abstract from PubMed 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. 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 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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