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Engineering and Characterisation of Bacterial Phosphopantetheinyl Transferases and their Peptide Substrates

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thesis
posted on 2021-11-22, 12:21 authored by Sissons, Jack Alexander

Throughout all domains of life, phosphopantetheinyl transferase (PPTase) enzymes catalyse a post-translational modification that is important in both primary and secondary metabolism; the transfer of a phosphopantetheine (PPant) group derived from Coenzyme A to specific protein domains within large, multi-modular biosynthetic enzymes, thereby activating each module for biosynthesis. The short peptide motif of the protein to which this group is attached is known as a ‘tag’, and can be fused to other proteins, making them also substrates for post-translational modification by a PPTase. Additionally, it has been demonstrated that PPTases can utilise a diverse range of CoA analogues, such as biotin-linked or click-chemistry capable CoA derivatives, as substrates for tag attachment. Together, these characteristics make post-translational modification by PPTases an attractive system for many different biotechnological applications. Perhaps the most significant application is in vivo and in vitro site-specific labelling of proteins, for which current technologies are hindered by cumbersome fusion protein requirements, toxicity of the process, or limited reporter groups that can be attached. Confoundingly, most PPTases exhibit a high degree of substrate promiscuity which limits the number of PPTase-tag pairs that can be used simultaneously, and therefore the number of protein targets that can be simultaneously labelled. To address this, directed evolution at a single gene level was used in an attempt to generate multiple PPTase variants that have non-overlapping tag specificity which have applications in orthogonal labelling. Furthermore, assays for the rapid identification, characterisation and evolution of short, novel peptide motifs that are recognised by PPTases has further diversified the labelling toolkit. These developments have enhanced the utility of the PPTase system and potentially have a wide range of applications in a number of fields.

History

Copyright Date

2017-01-01

Date of Award

2017-01-01

Publisher

Te Herenga Waka—Victoria University of Wellington

Rights License

Author Retains Copyright

Degree Discipline

Biotechnology

Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level

Masters

Degree Name

Master of Science

ANZSRC Type Of Activity code

970106 Expanding Knowledge in the Biological Sciences

Victoria University of Wellington Item Type

Awarded Research Masters Thesis

Language

en_NZ

Victoria University of Wellington School

School of Biological Sciences

Advisors

Ackerley, David