Master Degree / Yüksek Lisans Tezleri

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  • Master Thesis
    Expression, Purification and Preliminary Functional Characterization of the Acidianus Two-Tailed Virus Tnpb Endonucleases
    (01. Izmir Institute of Technology, 2024) Burgeia, Arwa Saleh; Oke, Muse
    TnpB is an RNA-guided endonuclease encoded in the IS200/605 transposon family. It forms a complex with a self-encoded ωRNA that directs TnpB to an appropriate target DNA sequence for activity. DNA cleavage at the target site promotes homologous recombination thus ensuring propagation of IS200/605 elements. Although IS200/605 elements are abundant in prokaryotic genomes, they are rarely found in viruses. However, the Acidianus two-tailed virus (ATV), which possesses 72 genes, encodes four TnpB proteins (gp10, gp40, gp43 and gp68). In this study, bioinformatics analysis of all ATV tnpB genes demonstrated that they were all solo tnpB genes and therefore could be classified as part of the IS1341 group. TnpB proteins are characterized by having a DED catalytic site motif and a C-terminal C4 zinc finger motif. Although the ATV gp10 protein retains the DED active site motif found in most TnpB proteins, the other ATV TnpB proteins possess a different amino acid instead of the Glu residue. Additionally, the ATV TnpB proteins possess the C4 zinc finger motif except for ATV gp40, which possesses three cysteine residues. All four ATV tnpB genes were cloned and expressed in the heterologous Escherichia coli host. The gp40 and gp68 proteins were purified using Ni2+ -NTA and gel filtration chromatography. Although gp68 appears to bind to DNA, there is insufficient evidence for RNA binding. Cleavage assays revealed that gp68 demonstrated nonspecific DNA nickase and cleavage activities. The significance of this study and the broader implications regarding the possible role of TnpB in virus survival are discussed.