Purification and structural characterization of a D-amino acid-containing conopeptide, conomarphin, from Conus marmoreus.
Cone snails, a group of gastropod animals that inhabit tropical seas, are capable of producing a mixture of peptide neurotoxins, namely conotoxins, for defense and predation. Conotoxins are mainly disulfide-rich short peptides that act on different ion channels, neurotransmitter receptors, or transporters in the nervous system. They exhibit highly diverse compositions, structures, and biological functions. In this work, a novel Cys-free 15-residue conopeptide from Conus marmoreus was purified and designated as conomarphin. Conomarphin is unique because of its D-configuration Phe at the third residue from the C-terminus, which was identified using HPLC by comparing native conomarphin fragments and the corresponding synthetic peptides cleaved by different proteases. Surprisingly, the cDNA-encoded precursor of conomarphin was found to share the conserved signal peptide with other M-superfamily conotoxins, clearly indicating that conomarphin should belong to the M-superfamily, although conomarphin shares no homology with other six-Cys-containing M-superfamily conotoxins. Furthermore, NMR spectroscopy experiments established that conomarphin adopts a well-defined structure in solution, with a tight loop in the middle of the peptide and a short 3(10)-helix at the C-terminus. By contrast, no loop in L-Phe13-conomarphin was found, which suggests that D-Phe13 is essential for the structure of conomarphin. In conclusion, conomarphin may represent a new conotoxin family, whose biological activity remains to be identified.
Han
Yuhong
Y
Institute of Protein Research, Tongji University, Shanghai, China.
Huang
Feijuan
F
Jiang
Hui
H
Liu
Li
L
Wang
Qi
Q
Wang
Yanfang
Y
Shao
Xiaoxia
X
Chi
Chengwu
C
Du
Weihong
W
Wang
Chunguang
C
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D020916:Conotoxins / Q000737:chemistry* / Q000302:isolation & purification*; D052078:Conus Snail / Q000737:chemistry*; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D008956:Models, Chemical; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry* / Q000302:isolation & purification*; D011487:Protein Conformation
D020916:Conotoxins; D018076:DNA, Complementary; D010455:Peptides; C529778:conomarphin, Conus marmoreus