Cytotoxic potency of small macrocyclic knot proteins : Structure-activity and mechanistic studies of native and chemically modified cyclotides

• The cyclotides are a family of circular and knotted proteins of natural origin with extreme enzymatic and thermal stability and active in a wide range of biological activities make them promising tools for pharmaceutical and crop-protection applications. The cyclotides are divided into two subfamilies depending on the presence (Möbius) or absence (bracelet) of a cis-Pro peptide bond. In the current work we report a series of experiments to give further insight into the structure activity relationship of cyclotides in general, and the differences between subfamilies and the role of their hydrophobic surface in particular. Selective chemical modifications of Glu, Arg, Lys and Trp residues was tested for cytotoxic activity and derivatives in which the Trp residue was modified showed low effect, suggesting the existence of a connection between hydrophobicity and activity. However, over the full set of cyclotides examined, there was no strong correlation between the cytotoxic activity and their hydrophobicity. Instead, it seems more like that the distribution of charged and hydrophobic residues determines the ultimate degree of potency. Furthermore, we found that while the Glu residue is very important in maintaining the activity of the bracelet cyclotide cycloviolacin O2, it is much less important in the Möbius cyclotides. However, despite these differences, a systematic test of mixtures of cyclotides, even from both subfamilies revealed that they act in an additive way.  

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Farmaceutiska vetenskaper (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Pharmaceutical Sciences (hsv//eng)

Nyckelord

Cyclotide

Additive effects

Cytotoxicity

PHARMACY

FARMACI

Publikations- och innehållstyp

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