Effect of Sulfur Binding on Rhodanese Fluorescence

Abstract

1.Intrinsic fluorescences of the sulfur-transferring protein rhodanese (or thiosulfate : cyanide sulfurtransferase) and of artificially persulfurated bovine serum albumin were studied. Both are attributable mainly to tryptophan side-chains. Addition of cyanide or sulfite to these proteins causes a 20-250/, increase in fluorescence.2. Both proteins exhibit a Iow intensity absorption band a t about 330 nm which disappears on addition of cyanide or sulfite. This absorption can be restored in rhodanese, after the treatment with cyanide, by excess thiosulfate ; in the same time the fluorescence decreases to that of sulfur-containing enzyme.3. A change in solvent viscosity, obtained by addition of glycerol, reduces the quenching effect in both proteins. On the basis of these data a long-range energy-transfer mechanism between the donor (tryptophan) and an acceptor is proposed. The acceptor involved seems to be one or more persulfide groups (R-SSH) in both proteins.

Differences in the binding of sulfate, selenate and thiosulfate ions to bovine liver rhodanese, and a description of a binding site for ammonium and sodium ions

“…These compounds bear direct relevance to the above-mentioned reaction: the latter as a substrate, the former as a competitive inhibitor. In the absence of sulfur-accepting agents like CN-, the enzyme will remain in a stable Rhod-S form, carrying an additional sulfur atom bound to Sy 247 as was revealed by earlier crystallographic investigations [ 11,121 in agreement with the results of spectroscopic studies [13].…”

“…These compounds bear direct relevance to the above-mentioned reaction: the latter as a substrate, the former as a competitive inhibitor. In the absence of sulfur-accepting agents like CN-, the enzyme will remain in a stable Rhod-S form, carrying an additional sulfur atom bound to Sy 247 as was revealed by earlier crystallographic investigations [ 11,121 in agreement with the results of spectroscopic studies [13].The studies on the structure of Rhod-S in a thiosulfate medium were initiated because of the report of a dead-end complex of Rhod-S . thiosulfate occurring during the catalytic cycle of the enzyme [14].…”

Enzymatic Activity of the Arabidopsis Sulfurtransferase Resides in the C-Terminal Domain But Is Boosted by the N-Terminal Domain and the Linker Peptide in the Full- Length Enzyme

“…After incubation with 4 M urea only 10% residual activity was found with STwlink but still 50% of activity with ST1. Obviously, the linker sequence plays not only an important role in providing a hydrophobic environment for substrate binding and catalysis as was shown previously (Finazzi Agro et al, 1972;MillerMartini et al, 1994a,b) but is also highly responsible for the overall stability of the ST protein. Table 1 and Figure 1 give an overview about the different clones containing amino acid replacements.…”

“…In this reaction rhodanese cycles between the sulfur-free (E) and sulfur-substituted (ES) form. Solution studies have identified three catalytic requirements: an active site sulfhydryl group, two cationic residues, and a hydrophobic environment for substrate binding (Finazzi Agro et al, 1972;Miller-Martini et al, 1994a,b).…”

Enzymic synthesis of the iron‐sulfur cluster of spinach ferredoxin

“…Evidence was also reported on the possible involvement of sulfurtransferascs, an ubiquitous class of enzymes [5,6], in the biosynthesis of iron-sulfur clusters [7,8]. 3-Mercaptopyruvate sulfurtransferase activity was found in both mitochondria and cytosol, but its involvement in the formation of the iron-sulfur cluster of adrenodoxin requires cysteine transaminase activity which is present almost only in the soluble fraction [7].…”