Isolation, solution structure, and insecticidal activity of kalata B2, a circular protein with a twist: Do Mobius strips exist in nature?

The three-dimensional structure determined using (super 1)H NMR spectroscopy is presented and the potent insecticidal activity for one of these peptides, kalata B2 is demonstrated. Examination of the sequence reveals that they could be separated in to two subfamilies, one of which contains a larger number of positively charged residues and has a bracelet-like circularization of the backbone, and the other contains a backbone twist due to a cis-peptidyl-proline bond and might conceptually be regarded as a molecular Mobius strip.