TY  - JOUR
A1  - Warelow, Thomas P.
A1  - Oke, Muse
A1  - Schoepp-Cothenet, Barbara
A1  - Dahl, Jan U.
A1  - Bruselat, Nicole
A1  - Sivalingam, Ganesh N.
A1  - Leimkühler, Silke
A1  - Thalassinos, Konstantinos
A1  - Kappler, Ulrike
A1  - Naismith, James H.
A1  - Santini, Joanne M.
T1  - The Respiratory Arsenite Oxidase: Structure and the Role of Residues
 Surrounding the Rieske Cluster
JF  - PLOS ONE
N2  - The arsenite oxidase (Aio) from the facultative autotrophic Alphaproteobacterium Rhizobium sp. NT-26 is a bioenergetic enzyme involved in the oxidation of arsenite to arsenate. The enzyme from the distantly related heterotroph, Alcaligenes faecalis, which is thought to oxidise arsenite for detoxification, consists of a large alpha subunit (AioA) with bis-molybdopterin guanine dinucleotide at its active site and a 3Fe-4S cluster, and a small beta subunit (AioB) which contains a Rieske 2Fe-2S cluster. The successful heterologous expression of the NT-26 Aio in Escherichia coli has resulted in the solution of its crystal structure. The NT-26 Aio, a heterotetramer, shares high overall similarity to the heterodimeric arsenite oxidase from A. faecalis but there are striking differences in the structure surrounding the Rieske 2Fe-2S cluster which we demonstrate explains the difference in the observed redox potentials (+225 mV vs. +130/160 mV, respectively). A combination of site-directed mutagenesis and electron paramagnetic resonance was used to explore the differences observed in the structure and redox properties of the Rieske cluster. In the NT-26 AioB the substitution of a serine (S126 in NT-26) for a threonine as in the A. faecalis AioB explains a -20 mV decrease in redox potential. The disulphide bridge in the A. faecalis AioB which is conserved in other betaproteobacterial AioB subunits and the Rieske subunit of the cytochrome bc(1) complex is absent in the NT-26 AioB subunit. The introduction of a disulphide bridge had no effect on Aio activity or protein stability but resulted in a decrease in the redox potential of the cluster. These results are in conflict with previous data on the betaproteobacterial AioB subunit and the Rieske of the bc(1) complex where removal of the disulphide bridge had no effect on the redox potential of the former but a decrease in cluster stability was observed in the latter.
Y1  - 2013
U6  - https://doi.org/10.1371/journal.pone.0072535
SN  - 1932-6203
VL  - 8
IS  - 8
PB  - PUBLIC LIBRARY SCIENCE
CY  - SAN FRANCISCO
ER  -