Structural and spectroscopic studies on the porin-cytochrome complex from Shewanella oneidensis MR-1

Lawes, Matthew (2015) Structural and spectroscopic studies on the porin-cytochrome complex from Shewanella oneidensis MR-1. Doctoral thesis, University of East Anglia.

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Abstract

The"outer"membrane,"hetero!trimeric"multi!heme"cytochrome"complex"MtrCAB,"enables"the"
process"of"dissimilatory"metal"reduction"(DMR)"in"Shewanella(oneidensis."
""
The"properties"of" the"decaheme"protein"MtrA"as"well"as"a" truncated"version"of" this"protein"
were" investigated" using" analytical" ultracentrifugation" (AUC)," small" angle" X!ray" scattering"
(SAXS)" and" spectropotentiometric" techniques." MtrA" and" a" truncated"N!terminal" MtrA"
construct"containing" the" five"N!terminal"hemes"(MtrA"N)"were"both"observed" to"be"prolate"
and"highly"extended" along"one" axis."Through" aligning"MtrA"N"with"MtrA," the"N" terminus" of"
the"MtrA"structure"was"identified.""Redox"titration"experiments"were"performed"on"MtrA"as"
well" as" N" and"C" terminal" truncations."From" these" titrations" three"distinct" groups" of" hemes"
were" identified;" a" high," a" middle" potential" and" a" low" potential" group" of" hemes." The" five"N"
terminal"hemes"contained"the"high"and"middle"potential"groups"of"hemes;"whereas"the"five"C"
terminal"hemes"contained"the"middle"and"low"potential"groups"of"hemes."
"
The"MtrCAB" complex"was" inserted" into" liposomes" containing" either"methyl" viologen," small"
tetra" heme" cytochrome" (STC)" or" cytochrome" c." Using" these" proteoliposomes" the" rate" of"
electron"transfer"across"MtrCAB"was"investigated."MtrCAB"was"seen"to"enable"the"reduction"
and"oxidation"of"methyl"viologen"and"STC,"but"only"the"reduction"of"cytochrome"c.""STC"was"
reduced" during" the" experiments," implying" an" electron" storage" role" in" the" periplasm"
during"respiration."
"Finally,"the" structure" of" MtrCAB" was" investigated" through" small" angle" neutron" scattering"
(SANS)."Structures"of"MtrCAB"were"highly"elongated"with"a"globular"head" region"and"a" tail"
region."Through"density"matching"buffers,"scattering"produced"from"detergents"was"removed"
and"a"prediction"of"the"relative"location"of"MtrB"within"the"model"made."The"model"produced"
was" found" to" be" long" enough" to" span" the" periplasm" enabling" direct" contact" of"MtrA" with"
proteins"on"the"inner"membrane.""

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Mia Reeves
Date Deposited: 28 Jan 2016 12:29
Last Modified: 28 Jan 2016 12:29
URI: https://ueaeprints.uea.ac.uk/id/eprint/56830
DOI:

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