2B38

Solution structure of kalata B8

Summary for 2B38

• Entry DOI: 10.2210/pdb2b38/pdb
• NMR Information: BMRB: 6872
• Descriptor: kalata B8 (1 entity in total)
• Functional Keywords: cyclic backbone, cystine knot, beta-hairpin, plant protein
• Biological source: Oldenlandia affinis
• Total number of polymer chains: 1
• Total formula weight: 3310.82

Authors

Daly, N.L.,Clark, R.J.,Plan, M.R.,Craik, D.J. (deposition date: 2005-09-19, release date: 2006-01-31, Last modification date: 2024-10-30)

Primary citation

Daly, N.L.,Clark, R.J.,Plan, M.R.,Craik, D.J.
Kalata B8, a novel antiviral circular protein, exhibits conformational flexibility in the cystine knot motif
Biochem.J., 393:619-626, 2006

PubMed Abstract: 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 (Möbius 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.

PubMed: 16207177
DOI: 10.1042/BJ20051371

Experimental method

SOLUTION NMR