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A new subfamily of conotoxins belonging to the A-superfamily.

ABSTRACT: Two novel conotoxins from vermivorous cone snails Conus pulicarius and Conus tessulatus, designated as Pu14.1 and ts14a, were identified by cDNA cloning and peptide purification, respectively. The signal sequence of Pu14.1 is identical to that of ?-conotoxins, while its predicted mature peptide, pu14a, shares high sequence similarity with ts14a, with only one residue different in their first intercysteine loop, which contains 10 residues and is rich in proline. Both pu14a and ts14a contain four separate cysteines in framework 14 (C-C-C-C). Peptide pu14a was chemically synthesized, air oxidized, and the connectivity of its two disulfide bonds was determined to be C1-C3, C2-C4, which is the same as found in ?-conotoxins. The synthetic pu14a induced a sleeping symptom in mice and was toxic to freshwater goldfish upon intramuscular injection. Using the Xenopus oocyte heterologous expression system, 1?M of pu14a demonstrated to inhibit the rat neuronal ?3?2-containing as well as the mouse neuromuscular ?1?1?? subtypes of nicotinic acetylcholine receptors, and then rapidly dissociated from the receptors. However, this toxin had no inhibitory effect on potassium channels in mouse superior cervical ganglion neurons. According to the identical signal sequence to ?-conotoxins, the unique cysteine framework and molecular target of pu14a, we propose that pu14a and ts14a may represent a novel subfamily in the A-superfamily, designated as ?1-conotoxins.

SUBMITTER: Peng C

PROVIDER: S-EPMC3721517 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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A new subfamily of conotoxins belonging to the A-superfamily.

Peng Can C Ye Mingyu M Wang Yanfang Y Shao Xiaoxia X Yuan Duoduo D Liu Jing J Hawrot Edward E Wang Chunguang C Chi Chengwu C

Peptides 20100804 11

Two novel conotoxins from vermivorous cone snails Conus pulicarius and Conus tessulatus, designated as Pu14.1 and ts14a, were identified by cDNA cloning and peptide purification, respectively. The signal sequence of Pu14.1 is identical to that of α-conotoxins, while its predicted mature peptide, pu14a, shares high sequence similarity with ts14a, with only one residue different in their first intercysteine loop, which contains 10 residues and is rich in proline. Both pu14a and ts14a contain four ...[more]

PMID: 20691232

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Project description:BACKGROUND: The CACTA (also called En/Spm) superfamily of DNA-only transposons contain the core sequence CACTA in their Terminal Inverted Repeats (TIRs) and so far have only been described in plants. Large transcriptome and genome sequence data have recently become publicly available for Schistosoma mansoni, a digenetic blood fluke that is a major causative agent of schistosomiasis in humans, and have provided a comprehensive repository for the discovery of novel genes and repetitive elements. Despite the extensive description of retroelements in S. mansoni, just a single DNA-only transposon belonging to the Merlin family has so far been reported in this organism. RESULTS: We describe a novel S. mansoni transposon named SmTRC1, for S. mansoni Transposon Related to CACTA 1, an element that shares several characteristics with plant CACTA transposons. Southern blotting indicates approximately 30-300 copies of SmTRC1 in the S. mansoni genome. Using genomic PCR followed by cloning and sequencing, we amplified and characterized a full-length and a truncated copy of this element. RT-PCR using S. mansoni mRNA followed by cloning and sequencing revealed several alternatively spliced transcripts of this transposon, resulting in distinct ORFs coding for different proteins. Interestingly, a survey of complete genomes from animals and fungi revealed several other novel TRC elements, indicating new families of DNA transposons belonging to the CACTA superfamily that have not previously been reported in these kingdoms. The first three bases in the S. mansoni TIR are CCC and they are identical to those in the TIRs of the insects Aedes aegypti and Tribolium castaneum, suggesting that animal TRCs may display a CCC core sequence. CONCLUSION: The DNA-only transposable element SmTRC1 from S. mansoni exhibits various characteristics, such as generation of multiple alternatively-spliced transcripts, the presence of terminal inverted repeats at the extremities of the elements flanked by direct repeats and the presence of a Transposase_21 domain, that suggest a distant relationship to CACTA transposons from Magnoliophyta. Several sequences from other Metazoa and Fungi code for proteins similar to those encoded by SmTRC1, suggesting that such elements have a common ancestry, and indicating inheritance through vertical transmission before separation of the Eumetazoa, Fungi and Plants.

Project description:BackgroundVectors of mosquito-borne diseases in Sri Lanka, except for malaria, belong to the subfamily Culicinae, which includes nearly 84% of the mosquito fauna of the country. Hence, accurate and precise species identification of culicine mosquitoes is a crucial factor in implementing effective vector control strategies. During the present study, a combined effort using morphology and DNA barcoding was made to characterize mosquitoes of the subfamily Culicinae for the first time from nine districts of Sri Lanka. Cytochrome c oxidase subunit 1 (cox1) gene from the mitochondrial genome and the internal transcribed spacer 2 (ITS2) region from the nuclear ribosomal DNA were used for molecular characterization.ResultsAccording to morphological identification, the field collected adult mosquitoes belonged to 5 genera and 14 species, i.e. Aedes aegypti, Ae. albopictus, Ae. pallidostriatus, Aedes sp. 1, Armigeres sp. 1, Culex bitaeniorhynchus, Cx. fuscocephala, Cx. gelidus, Cx. pseudovishnui, Cx. quinquefasciatus, Cx. tritaeniorhynchus, Cx. whitmorei, Mansonia uniformis and Mimomyia chamberlaini. Molecular analyses of 62 cox1 and 36 ITS2 sequences were exclusively comparable with the morphological identifications of all the species except for Ae. pallidostriatus and Aedes sp. 1. Although the species identification of Armigeres sp. 1 specimens using morphological features was not possible during this study, DNA barcodes of the specimens matched 100% with the publicly available Ar. subalbatus sequences, giving their species status. Analysis of all the cox1 sequences (14 clades supported by strong bootstrap value in the Neighbor-Joining tree and interspecific distances of > 3%) showed the presence of 14 different species. This is the first available DNA sequence in the GenBank records for morphologically identified Ae. pallidostriatus. Aedes sp. 1 could not be identified morphologically or by publicly available sequences. Aedes aegypti, Ae. albopictus and all Culex species reported during the current study are vectors of human diseases. All these vector species showed comparatively high diversity.ConclusionsThe current study reflects the significance of integrated systematic approach and use of cox1 and ITS genetic markers in mosquito taxonomy. Results of DNA barcoding were comparable with morphological identifications and, more importantly, DNA barcoding could accurately identify the species in the instances where the traditional morphological identification failed due to indistinguishable characters of damaged specimens and the presence of subspecies.

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A new subfamily of conotoxins belonging to the A-superfamily.

Publications

A new subfamily of conotoxins belonging to the A-superfamily.

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