Biophysical and structural studies of insect virus polyhedra

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dc.contributor.advisor Metcalf, P. en
dc.contributor.advisor Baker, T. en Chiu, Yui Lam Elaine en 2020-06-02T04:32:30Z en 2020-06-02T04:32:30Z en 2008 en
dc.identifier.uri en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract Polyhedra are the intracellular protein micro-crystals that form within larvae infected by either of the unrelated insect viruses cypovirus or baculovirus. The naturally occurring infective forms of these viruses are polyhedra, ~1-3 micron micro-crystals that incorporate numerous virus particles as they grow within infected midgut epithelial cells. Polyhedra are very stable and remain infectious in the environment for many years, but dissolve readily after ingestion by larvae releasing the encapsulated virus particles. Polyhedra are composed mainly of a single virus-encoded protein polyhedrin. Despite the different origins of the two viruses (cypovirus is a dsRNA virus, baculovirus is a dsDNA virus) and the lack of sequence homology between the polyhedrins, both types of polyhedra are organised in body-centred cubic lattices with similar unit cell dimensions ~103 Å. In this work polyhedra obtained from diseased larvae or produced using the baculovirus protein expression system, were investigated using a variety of techniques including microscopy, mass spectrometry, CD spectroscopy and protein X-ray crystallography. Methods were developed to collect single-crystal diffraction data using a specialised synchrotron micro-beam X-ray source. Diffraction data from native, SeMet-substituted and heavy atom-soaked polyhedra were used to determine the atomic structures of both cypovirus Bombyxmori BmCPV polyhedra, and baculovirus Autographa californica AcMNPV-G25D polyhedra. The structures revealed that both polyhedra are organised as trimers of polyhedrins with similar overall triangular shape. Despite this and the essentially identical cubic unit cell dimensions, the detailed atomic structure of the two polyhedrins is quite different. The central core of AcMNPV-G25D polyhedrin is arranged as a jelly roll fold, while BmCPV polyhedrin has a novel fold. Experiments were also carried out to investigate the remarkable stability of polyhedra and to produce polyhedral using a bacterial expression system. The results may lead in future to the development of stable engineered polyhedra for a variety of biotechnology or medical applications. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA99185059514002091 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
dc.rights Restricted Item. Full text is available to authenticated members of The University of Auckland only. en
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dc.title Biophysical and structural studies of insect virus polyhedra en
dc.type Thesis en Biological Sciences en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The author en

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