Evolutionary origin of inhibitor cystine knot peptides.
The inhibitor cystine knot (ICK) fold is an evolutionarily conserved structural motif shared by a large group of polypeptides with diverse sequences and bioactivities. Although found in different phyla (animal, plant, and fungus), ICK peptides appear to be most prominent in venoms of cone snail and spider. Recently, two scorpion toxins activating a calcium release channel have been found to adopt an ICK fold. We have isolated and identified both cDNA and genomic clones for this family of ICK peptides from the scorpion Opistophthalmus carinatus. The gene characterized by three well-delineated exons respectively coding for three structural and functional domains in the toxin precursors illustrates the correlation between exon and module as suggested by the "exon theory of genes." Based on the analysis of precursor organization and gene structure combined with the 3-D fold and functional data, our results highlight a common evolutionary origin for ICK peptides from animals. In contrast, ICK peptides from plant and fungus might be independently evolved from another ancestor.
Zhu
Shunyi
S
Laboratory of Toxicology, University of Leuven, Belgium.
Darbon
Herve
H
Dyason
Karin
K
Verdonck
Fons
F
Tytgat
Jan
J
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D003553:Cystine / Q000737:chemistry; D019143:Evolution, Molecular; D040461:Gene Components; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000235:genetics*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics; D011487:Protein Conformation; D011498:Protein Precursors / Q000737:chemistry / Q000235:genetics; D012604:Scorpion Venoms / Q000737:chemistry / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics
D010455:Peptides; D010940:Plant Proteins; D011498:Protein Precursors; D012604:Scorpion Venoms; D014764:Viral Proteins; D003553:Cystine