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Title: X-ray crystallographic studies on Particulate Methane Monooxygenase, Thioredoxin A and Arginine Decarboxylase
Author: Andrell, Juni
ISNI:       0000 0004 2677 7192
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2008
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The work presented in this thesis describes the X-ray crystallographic studies of particulatemethane monoxygenase (pMMO) from Methylococcus capsulatus (Bath), thioredoxin A(BsTrxA) from Bacillus subtilis and arginine decarboxylase (AdiA) from Escherichia coli.1. pMMO is a respiratory enzyme that catalyses the first step in the metabolic pathway inmethanotrophic bacteria by converting methane to methanol. The crystal structure of thisintegral membrane protein was determined by molecular replacement to 3.5 ? resolution. The three metal sites in pMMO were confirmed to be a mononuclear copper site, adinuclear copper site and a mononuclear zinc site.2. Thioredoxin is a ubiquitous protein present in nearly all known organisms. Its purposein the cell is to maintain cysteine-containing proteins in the reduced state by convertingintramolecular disulfide bonds to dithiols in a redox reaction. The crystal structure of anactive site mutant of BsTrxA was determined by molecular replacement to 1.5 ?resolution. The structure shows a homodimer that resembles enzyme-substrate reactionintermediates.3. AdiA is a vitamin B6-dependent enzyme that catalyses the decarboxylation of arginineinto agmatine. It forms a part of an enzymatic system in E. coli that contribute to makingthis organism acid resistant. The structure of arginine decarboxylase (AdiA) from E. coliwas determined by multiple isomorphous replacement and anomalous scattering (MIRAS)methods to 2.4 ? resolution. The structure revealed a ~800 kDa decamer composed as apentamer of five homodimers. AdiA becomes active as the cellular environment becomesmore acidic. The structure of AdiA suggests how functional decamers associate withdecreasing pH or disassociates into inactive homodimers with increasing pH. The enzymemechanism and determinants for substrate specificity are discussed within the frameworkof the structure and comparisons with related structures are made.
Supervisor: Carpenter, Liz ; Iwata, So Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral