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

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.""

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2015

Author dc:creator

• Lawes, Matthew

Language dc:language

en