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Expression and structural studies of multidomain proteins and complexes

Chamberlain, Dean; (1998) Expression and structural studies of multidomain proteins and complexes. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

It is generally accepted that there is a level of organization in proteins that overlaps the classical definitions of tertiary and quaternary structure, i.e. sequentially consecutive residues in polypeptide chains fold into distinct compact regions called domains. Many multidomain proteins are flexible and are not amenable to X-ray crystallography or are too big for multi dimensional nuclear magnetic resonance techniques, while other proteins form oligomeric structures from subunits. It is possible using small-angle X-ray and neutron scattering, coupled with molecular modelling techniques, to locate the relative positions of these domains or subunits relative to each other within the full protein structure. This PhD thesis has looked at a variety of native and recombinant oligomeric proteins and domains and attempts have been made to produce low resolution structures of their oligomerisation or their multidomain structures. Expression systems used include a Pseudomonas aeruginosa over-expression system and the baculovirus expression system. One multidomain protein was studied, namely factor I of the complement system. Two forms of factor I were studied, a native form purified from human plasma, and a recombinant form produced in insect cells. Scattering modelling was used to elucidate a bilobal domain arrangement in factor I, in which the different types of carbohydrate present on the two different forms could be modelled. The quaternary structures of two complexes were determined, namely the homo- oligomeric complexes of the Ps. aeruginosa amidase regulatory protein, AmiC, and the Mycobacterium leprae Holliday junction protein, RuvA. It was determined that in solution AmiC exists as a monomer-trimer equilibrium, and that RuvA adopts an octameric structure, both when lice and when complexed with DNA, within which the Holliday junction is buried in the RuvA-DNA complex.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Expression and structural studies of multidomain proteins and complexes
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences; Oligomeric proteins
URI: https://discovery.ucl.ac.uk/id/eprint/10121848
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