5k3x

Crystal Structure of the sulfite dehydrogenase, SorT R78K mutant from Sinorhizobium meliloti

spinqualitylabelsall models 5k3x, resolution 1.60Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 5k3x is a 2 chain structure with sequence from Sinorhizobium meliloti 1021. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.6Å Ligands: GOL, MSS Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q92M24_RHIME The exact function is not known. Can catalyze the reduction of a variety of substrates like dimethyl sulfoxide, trimethylamine N-oxide, phenylmethyl sulfoxide and L-methionine sulfoxide. Cannot reduce cyclic N-oxides. Shows no activity as sulfite oxidase.[SAAS:SAAS00086612] Publication Abstract from PubMed A central conserved arginine, first identified as a clinical mutation leading to sulfite oxidase deficiency, is essential for catalytic competency of sulfite oxidizing molybdoenzymes, but the molecular basis for its effects on turnover and substrate affinity have not been fully elucidated. We have used a bacterial sulfite dehydrogenase, SorT, which lacks an internal heme group, but transfers electrons to an external, electron accepting cytochrome, SorU, to investigate the molecular functions of this arginine residue (Arg78). Assay of the SorT Mo centre catalytic competency in the absence of SorU showed that substitutions in the central arginine (R78Q, R78K and R78M mutations) only moderately altered SorT catalytic properties, except for R78M which caused significant reduction in SorT activity. The substitutions also altered the Mo-centre redox potentials (MoVI/V potential lowered by ca. 60-80mV). However, all Arg78 mutations significantly impaired the ability of SorT to transfer electrons to SorU, where activities were reduced 17 to 46-fold compared to SorTWT, precluding determination of kinetic parameters. This was accompanied by the observation of conformational changes in both the introduced Gln and Lys residues in the crystal structure of the enzymes. Taking into account data collected by others on related SOE mutations we propose that the formation and maintenance of an electron transfer complex between the Mo centre and electron accepting heme groups is the main function of the central arginine, and that the reduced turnover and increases in KMsulfite are caused by the inefficient operation of the oxidative half reaction of the catalytic cycle in enzymes carrying these mutations. The central active site arginine in sulfite oxidizing enzymes alters kinetic properties by controlling electron transfer and redox interactions.,Hsiao JC, McGrath AP, Kielmann L, Kalimuthu P, Darain F, Bernhardt PV, Harmer J, Lee M, Meyers K, Maher MJ, Kappler U Biochim Biophys Acta. 2017 Oct 3. pii: S0005-2728(17)30147-0. doi:, 10.1016/j.bbabio.2017.10.001. PMID:28986298 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

Proteopedia Page Contributors and Editors (what is this?)

OCA