Production and characterization of DNA ligases isolated from Kogelberg Biosphere metagenomics library.
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Date
2021
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Abstract
Microbial enzymes have been described as an underutilized source of novel enzymes with
potential economic advantages. Recently discovered enzymes such as DNA ligase from
metagenomic studies, have been shown to achieve great potential in transforming the reagent
market specifically in the African continent. Reagent proteins are frequently utilized in the
research field widely and are prone to protein degradation and shelf-life reduction. Hence,
this study sought to improve biological activity, shelf life and stability of the two DNA
ligases identified from Kogelberg Biosphere metagenomics library. Two recombinant DNA
ligases expression studies were done using E.coli BL21 and purification studies were done
subsequently using affinity chromatography. Both recombinant DNA ligases (Ligsv081 &
LigpET30) were successfully expressed and purified as homogenous proteins. In this study
two approaches were used to enhance the biological DNA ligases, the first approach used was
PEGylation. The purified proteins were conjugated to PEG using site-specific PEGylation
and non-specific PEGylation. FTIR and UV-VIS spectroscopy were used to analyze the
secondary structure of the PEG conjugated DNA ligases. Thermal stability assays were then
employed to assess protein stability in the conjugation with PEG. Site-specific PEGylation
enhanced ligase activity and reduced the formation of protein aggregates. The second
approach involved DNA ligase co-expression in the presence of PfHsp70 or chimeric
transcription factor, respectively. Protein co-expression and co-purification assays were
conducted. The co-expression and co-purification assays of both proteins with chimeric
transcription factor (cTF) were successful, followed by co-expression and co-purification of
LigpET30-PfHsp70. Ligation assays were conducted to assess bioactivity of proteins. All
DNA ligase complexes were functional and their melting point was increased. Taken
together, site-specific PEGylation and protein co-expression with PfHsp70 potentially
extended the shelf-life and stability of the proteins. PEGylation strategies and co-expression
strategies can potentially be used to enhance reagents in diagnostic and therapeutic tools in
molecular biology field.
Description
Masters Degree. University of KwaZulu-Natal, Durban.