The three-dimensional structure of an H-superfamily conotoxin reveals a granulin fold arising from a common ICK cysteine framework

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Lau D Nielsen, Mads M. Foged, Anastasia Albert, Andreas B. Bertelsen, Cecilie L Søltoft, Samuel D. Robinson, Steen Vang Petersen, Anthony W. Purcell, Baldomero M. Olivera, Raymond S. Norton, Terje Vasskog, Helena Safavi-Hemami, Kaare Teilum, Lars Ellgaard

Venomous marine cone snails produce peptide toxins (conotoxins) that bind ion channels and receptors with high specificity and therefore are important pharmacological tools. Conotoxins contain conserved cysteine residues that form disulfide bonds that stabilize their structures. To gain structural insight into the large, yet poorly characterized conotoxin H-superfamily, we used NMR and CD spectroscopy along with MS-based analyses to investigate H-Vc7.2 from Conus victoriae, a peptide with a VI/VII cysteine framework. This framework has CysI-CysIV/CysII-CysV/CysIII-CysVI connectivities, which have invariably been associated with the inhibitor cystine knot (ICK) fold. However, the solution structure of recombinantly expressed and purified H-Vc7.2 revealed that although it displays the expected cysteine connectivities, H-Vc7.2 adopts a different fold consisting of two stacked β-hairpins with opposing β-strands connected by two parallel disulfide bonds, a structure homologous to the N-terminal region of the human granulin protein. Using structural comparisons, we subsequently identified several toxins and nontoxin proteins with this "mini-granulin" fold. These findings raise fundamental questions concerning sequence-structure relationships within peptides and proteins and the key determinants that specify a given fold.

Original languageEnglish
JournalThe Journal of Biological Chemistry
Volume294
Issue number22
Pages (from-to)8745-8759
ISSN0021-9258
DOIs
Publication statusPublished - 2019

ID: 216519177