
@article {136528,
	title = {Cysteine-free cone snail venom peptides: Classification of precursor proteins and identification of mature peptides.},
	journal = {J Pept Sci},
	year = {2023},
	month = {2023 Nov 27},
	pages = {e3554},
	abstract = {<p>The cysteine-free acyclic peptides present in marine cone snail venom have been much less investigated than their disulfide bonded counterparts. Precursor protein sequences derived from transcriptomic data, together with mass spectrometric fragmentation patterns for peptides present in venom duct tissue extracts, permit the identification of mature peptides. Twelve distinct gene superfamiles have been identified with precursor lengths between 64 and 158 residues. In the case of Conus monile, three distinct mature peptides have been identified, arising from two distinct protein precursors. Mature acyclic peptides are often post-translationally modified, with C-terminus amidation, a feature characteristic of neuropeptides. In the present study, 20 acyclic peptides from Conus monile and Conus betulinus were identified. The common modifications of C-terminus amidation, gamma carboxylation of glutamic acid (E to ϒ), N-terminus conversion of Gln (Q) to a pyroglutamyl residue (Z), and hydroxylation of Pro (P) to Hyp (O) are observed in one or more peptides identified in this study. Proteolytic trimming of sequences by cleavage at the C-terminus of Asn (N) residues is established. The presence of an asparagine endopeptidase is strengthened by the identification of legumain-like sequences in the transcriptome assemblies from diverse Conus species. Such sequences may be expected to have a cleavage specificity at Asn-Xxx peptide bonds.</p>
},
	issn = {1099-1387},
	doi = {10.1002/psc.3554},
	author = {Vijayasarathy, Marimuthu and Kumar, Sanjeev and Das, Rajdeep and Balaram, Padmanabhan}
}
@article {45433,
	title = {Cone Snail Glutaminyl Cyclase Sequences from Transcriptomic Analysis and Mass Spectrometric Characterization of Two Pyroglutamyl Conotoxins.},
	journal = {J Proteome Res},
	volume = {17},
	year = {2018},
	month = {2018 Aug 03},
	pages = {2695-2703},
	abstract = {<p>The post-translational modification of N-terminal glutamine (Q) to a pyroglutamyl (Z) residue is observed in the conotoxins produced by marine cone snails. This conversion requires the action of the enzyme glutaminyl cyclase (QC). Four complete QC sequences from the species C. araneosus, C. frigidus, C. litteratus, and C. monile and two partial sequences from C. amadis and C. miles have been obtained by analysis of transcriptomic data. Comparisons with mammalian enzyme sequences establish a high level of identity and complete conservation of functional active site residues, including a cluster of hydrogen-bonded acidic side chains. Mass spectrometric analysis of crude venom samples coupled to conotoxin precursor protein sequences obtained from transcriptomic data establishes the presence of pyroglutamyl conotoxins in the venom of C. frigidus and C. amadis. The C. frigidus peptide belongs to the M superfamily, with cysteine framework III, whereas the C. amadis peptide belongs to the divergent superfamily with cysteine framework VI/VII. Additionally, gamma carboxylation of glutamic acid and hydroxylation of proline are observed in the C. frigidus peptide. Mass spectral data are available via ProteomeXchange with identifier PXD009006.</p>
},
	issn = {1535-3907},
	doi = {10.1021/acs.jproteome.8b00132},
	author = {Vijayasarathy, Marimuthu and Basheer, Soorej M and Balaram, Padmanabhan}
}
