The cyclotides have been recognised as a family of novel circular
proteins only in the last few years but the discovery of the first
member of this family may be traced back to reports of native
medicine applications in the early 1970s.
affinis was used by native women in the Zaire as an aid
during childbirth. A tea was made of the leaves and imbibed
Kalata B1, was discovered because it is an active ingredient in
a herbal medicine used by African women to assist childbirth
. While on a Red Cross relief effort in the Congo region in the
1960s a Norwegian doctor, Lorents Gran, noted that during labour
African women often ingested a tea made from leaves of the plant
Oldenlandia affinis because of its uterotonic effects. The active
ingredient was determined to be a peptide that was named kalata
B1, after the local name for the native medicine. Subsequent in
vivo studies in rats confirmed uterotonic activity of the purified
peptide but it was not characterised as a macrocyclic peptide
until some 20 year later.
The mid-1990’s was a key period in the discovery of
macrocyclic peptides, with several independent groups discovering
such peptides while screening for various biological activities
and our group determining the three dimensional structure of
kalata B1 . In the first fortuitous discovery Schöpke et al.,
examined Viola arvensis and V. tricolor in a study aimed at the
discovery of new saponins. While assaying for the usual hemolytic
activity of saponins they discovered a macrocyclic peptide,
violapeptide I, with hemolytic activity. At around the same time
bio-assay driven screens for anti-HIV and anti-neurotensin
activity led to the discovery of the circulins and
cyclopsychotride A respectively.
With our report of the three dimensional structure of kalata B1 in
1995 and its sequence homology with the circulins and
cyclopsychotride A, we became convinced that macrocyclic peptides
might be more common than had earlier been thought and we began
searching for other examples. Several other macrocyclic peptides
were found in the late 1990s and it became clear that the peptides
formed part of a family that we subsequently named the
| Viola arvensis a cyclotide
containing plant. Member of the violaceae family and found in
temperate regions of Australia and Europe.
Several novel cyclotide sequences have been discovered in the
last few years , with the known sequences now exceeding 45 and
many more currently being characterized in our laboratories. A
large proportion of the new cyclotides have been discovered based
on their structural properties rather than biological
activities. The cyclotides are relatively hydrophobic and can be
readily identified from crude plant extracts by their
characteristically late elution on RP-HPLC.
The cyclotides described above, all come from plants in the
Rubiaceae or Violaceae families but the prevalence of macrocyclic
peptides has recently been expanded to include the Cucurbitaceae
family. This is based on the discovery of the trypsin inhibitors
MCoTI-I and MCoTI-II, 34 residue macrocyclic peptides, from
Momordica cochinchinensis . They have no sequence homology to the
previously characterized cyclotides, with the exception of the six
cysteine residues, but are of a similar size and contain a cystine
knot motif (Felizmenio-Quimio, 2001). The MCoTI peptides were
originally isolated based on their trypsin inhibitory activity and
are homologous to linear cystine knot peptides from the squash
family of trypsin inhibitors such as EETI-II and CMTI.
Bokesch HR, Pannell LK, Cochran PK, Sowder RC, 2nd, McKee TC and
Boyd MR: A novel anti-HIV macrocyclic peptide from Palicourea
condensata. J. Nat. Prod. (2001) 64:249-250.
Broussalis AM, Goransson U, Coussio JD, Ferraro G, Martino V and
Claeson P: First cyclotide from Hybanthus
(Violaceae). Phytochemistry (2001) 58:47-51.
Claeson P, Göransson U, Johansson S, Luijendijk T and Bohlin L:
Fractionation protocol for the isolation of polypeptides from
plant biomass. J. Nat. Prod. (1998) 61:77-81.
Craik DJ, Daly NL, Bond T and Waine C: Plant cyclotides: A unique
family of cyclic and knotted proteins that defines the cyclic
cystine knot structural motif. J. Mol. Biol. (1999)
Göransson U, Luijendijk T, Johansson S, Bohlin L and Claeson P:
Seven novel macrocyclic polypeptides from Viola
arvensis. J. Nat. Prod. (1999) 62:283-286.
Gran L: Isolation of oxytocic peptides from Oldenlandia affinis by
solvent extraction of tetraphenylborate complexes and
chromatography on sephadex LH-20. Lloydia (1973a)
Gran L: On the effect of a polypeptide isolated from
"Kalata-Kalata" (Oldenlandia affinis DC) on the oestrogen
dominated uterus. Acta Pharmacol. Toxicol. (1973b)
Gustafson KR, Sowder II RC, Henderson LE, Parsons IC, Kashman Y,
Cardellina II JH, McMahon JB, Buckheit Jr. RW, Pannell LK and Boyd
MR: Circulins A and B: Novel HIV-inhibitory macrocyclic peptides
from the tropical tree Chassalia
parvifolia. J. Am. Chem. Soc. (1994)
Hallock YF, Sowder RCI, Pannell LK, Hughes CB, Johnson DG,
Gulakowski R, Cardellina JHI and Boyd MR: Cycloviolins A-D,
anti-HIV macrocyclic peptides from Leonia
cymosa. J. Org. Chem. (2000) 65:124-128.
Hernandez JF, Gagnon J, Chiche L, Nguyen TM, Andrieu JP, Heitz A,
Trinh Hong T, Pham TT and Le Nguyen D: Squash trypsin inhibitors
from Momordica cochinchinensis exhibit an atypical macrocyclic
structure. Biochemistry (2000) 39:5722-5730.
Saether O, Craik DJ, Campbell ID, Sletten K, Juul J and Norman DG:
Elucidation of the primary and three-dimensional structure of the
uterotonic polypeptide kalata B1. Biochemistry (1995)
Schöpke T, Hasan Agha MI, Kraft R, Otto A and Hiller K:
Hämolytisch aktive komponenten aus Viola tricolor L. und Viola
arvensis Murray. Sci. Pharm. (1993) 61:145-153.
Witherup KM, Bogusky MJ, Anderson PS, Ramjit H, Ransom RW, Wood T
and Sardana M: Cyclopsychotride A, A biologically active,
31-residue cyclic peptide isolated from Psychotria
Longipes. J. Nat. Prod. (1994) 57:1619-1625.