Newly Discovered Peptides from the Coral Heliofungia actiniformis Show Structural and Functional Diversity.

Scleractinian corals are crucially important to the health of some of the world's most biodiverse, productive, and economically important marine habitats. Despite this importance, analysis of coral peptidomes is still in its infancy. Here we show that the tentacle extract from the stony coral Heliofungia actiniformis is rich in peptides with diverse and novel structures. We have characterized the sequences and three-dimensional structures of four new peptides, three of which have no known homologues. We show that a 2 kDa peptide, Hact-2, promotes significant cell proliferation on human cells and speculate this peptide may be involved in the remarkable regenerative capacity of corals. We found a 3 kDa peptide, Hact-3, encoded within a fascin-like domain, and homologues of Hact-3 are present in the genomes of other coral species. Two additional peptides, Hact-4 and Hact-SCRiP1, with limited sequence similarity, both contain a beta-defensin-like fold and highlight a structural link with the small cysteine-rich proteins (SCRiP) family of proteins found predominantly in corals. Our results provide a first glimpse into the remarkable and unexplored structural diversity of coral peptides, providing insight into their diversity and putative functions and, given the ancient lineage of corals, potential insight into the evolution of structural motifs.