Sequencing of T-superfamily conotoxins from Conus virgo: Pyroglutamic acid identification and disulfide arrangement by MALDI mass spectrometry

Mandal, Amit Kumar and Ramasam, Mani Ramakrishnan Santhana and Sabareesh, Varatharajan and Openshaw, Matthew E and Krishnan, Kozhalmannom S and Balaram, Padmanabhan (2007) Sequencing of T-superfamily conotoxins from Conus virgo: Pyroglutamic acid identification and disulfide arrangement by MALDI mass spectrometry. In: Journal of the American Society for Mass Spectrometry, 18 (8). 1396-.

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Abstract

De novo mass spectrometric sequencing of two Conus peptides, Vi1359 and Vi1361, from the vermivorous cone snail Conus virgo, found off the southern Indian coast, is presented. The peptides, whose masses differ only by 2 Da, possess two disulfide bonds and an amidated C-terminus. Simple chemical modifications and enzymatic cleavage coupled with matrix assisted laser desorption ionization (MALDI) mass spectrometric analysis aided in establishing the sequences of Vi1359, ZCCITIPECCRI-NH2, and Vi1361, ZCCPTMPECCRI-NH2, Which differ only at residues 4 and 6 (Z = pyroglutamic acid). The presence of the pyroglutamyl residue at the N-terminus was unambiguously identified by chemical hydrolysis of the cyclic amide, followed by esterification. The presence of Ile residues in both the peptides was confirmed from high-energy collision induced dissociation (CID) studies, using the observation Of W-n- and d(n)-ions as a diagnostic. Differential cysteine labeling, in conjunction with MALDI-MS/MS, permitted establishment of disulfide connectivity in both peptides as Cys2-Cys9 and Cys3-Cys10. The cysteine pattern clearly reveals that the peptides belong to the class of T-superfamily conotoxins, in particular the T-1 superfamily.

Item Type:	Journal Article
Publication:	Journal of the American Society for Mass Spectrometry
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	posttranslational modifications;cdna cloning; marine snail; peptides;venom;channels;textile;fragmentation;proteomics; marmoreus.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	28 Apr 2010 06:38
Last Modified:	19 Sep 2010 06:00
URI:	http://eprints.iisc.ac.in/id/eprint/27332

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