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  1. Fulltext Mutagenesis and functional analysis of the pore-forming toxin HALT-1 from Hydra magnipapillata
    Liew YJ, Soh WT, Jiemy WF, Hwang JS
    Toxins (Basel), 2015 Feb;7(2):407-22.
    PMID: 25654788 DOI: 10.3390/toxins7020407
    Actinoporins are small 18.5 kDa pore-forming toxins. A family of six actinoporin genes has been identified in the genome of Hydra magnipapillata, and HALT-1 (Hydra actinoporin-like toxin-1) has been shown to have haemolytic activity. In this study, we have used site-directed mutagenesis to investigate the role of amino acids in the pore-forming N-terminal region and the conserved aromatic cluster required for cell membrane binding. A total of 10 mutants of HALT-1 were constructed and tested for their haemolytic and cytolytic activity on human erythrocytes and HeLa cells, respectively. Insertion of 1-4 negatively charged residues in the N-terminal region of HALT-1 strongly reduced haemolytic and cytolytic activity, suggesting that the length or charge of the N-terminal region is critical for pore-forming activity. Moreover, substitution of amino acids in the conserved aromatic cluster reduced haemolytic and cytolytic activity by more than 80%, suggesting that these aromatic amino acids are important for attachment to the lipid membrane as shown for other actinoporins. The results suggest that HALT-1 and other actinoporins share similar mechanisms of pore formation and that it is critical for HALT-1 to maintain an amphipathic helix at the N-terminus and an aromatic amino acid-rich segment at the site of membrane binding.
  2. Fulltext Complete mitochondrial genome of Dacus vijaysegarani and phylogenetic relationships with congeners and other tephritid fruit flies (Insecta: Diptera)
    Yong HS, Chua KO, Song SL, Liew YJ, Eamsobhana P, Chan KG
    Mol Biol Rep, 2021 Aug;48(8):6047-6056.
    PMID: 34357549 DOI: 10.1007/s11033-021-06608-2
    BACKGROUND: Tephritid fruit flies of the genus Dacus are members of the tribe Dacini, subfamily Dacinae. There are some 274 species worldwide, distributed in Africa and the Asia-Pacific. To date, only five complete mitochondrial genomes (mitogenomes) of Dacus fruit flies have been published and are available in the GenBank.

    METHODS AND RESULTS: In view of the lack of study on their mitogenome, we sequenced (by next generation sequencing) and annotated the complete mitogenome of D. vijaysegarani from Malaysia to determine its features and phylogenetic relationship. The whole mitogenome of D. vijaysegarani has identical gene order with the published mitogenomes of the genus Dacus, with 13 protein-coding genes, two rRNA genes, 22 tRNAs, a non-coding A + T rich control region, and intergenic spacer and overlap sequences. Phylogenetic analysis based on 15 mitochondrial genes (13 PCGs and two rRNA genes), reveals Dacus, Zeugodacus and Bactrocera forming a distinct clade. The genus Dacus forms a monophyletic group in the subclade containing also the Zeugodacus group; this Dacus-Zeugodacus subclade is distinct from the Bactrocera subclade. D. (Mellesis) vijaysegarani forms a lineage with D. (Mellesis) trimacula in the subcluster containing also the lineage of D. (Mellesis) conopsoides and D. (Callantra) longicornis. D. (Dacus) bivittatus and D. (Didacus) ciliatus form a distinct subcluster. Based on cox1 sequences, the Malaysia and Vietnam taxa of D. vijaysegarani may not be conspecific.

    CONCLUSIONS: Overall, the mitochondrial genome of D. vijaysegarani provided essential molecular data that could be useful for further studies for species diagnosis, evolution and phylogeny research of other tephritid fruit flies in the future.

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