4AAY

Crystal Structure of the arsenite oxidase protein complex from Rhizobium species strain NT-26

Summary for 4AAY

• Entry DOI: 10.2210/pdb4aay/pdb
• Descriptor: AROA, AROB, 2-AMINO-5,6-DIMERCAPTO-7-METHYL-3,7,8A,9-TETRAHYDRO-8-OXA-1,3,9,10-TETRAAZA-ANTHRACEN-4-ONE GUANOSINE DINUCLEOTIDE, ... (8 entities in total)
• Functional Keywords: oxidoreductase, rieske, iron sulfur, molybdopterin
• Biological source: ARSENITE-OXIDISING BACTERIUM NT-26; More
• Total number of polymer chains: 8
• Total formula weight: 455263.33

Authors

Oke, M.,Santini, J.M.,Naismith, J.H. (deposition date: 2011-12-05, release date: 2012-12-12, Last modification date: 2023-12-20)

Primary citation

Warelow, T.P.,Oke, M.,Schoepp-Cothenet, B.,Dahl, J.U.,Bruselat, N.,Sivalingam, G.N.,Leimkuhler, S.,Thalassinos, K.,Kappler, U.,Naismith, J.H.,Santini, J.M.
The Respiratory Arsenite Oxidase: Structure and the Role of Residues Surrounding the Rieske Cluster.
Plos One, 8:72535-, 2013

PubMed Abstract: 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 α subunit (AioA) with bis-molybdopterin guanine dinucleotide at its active site and a 3Fe-4S cluster, and a small β 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.

PubMed: 24023621
DOI: 10.1371/JOURNAL.PONE.0072535

Experimental method

X-RAY DIFFRACTION (2.7 Å)