The single cysteine residue of the Sud protein is required for its function as a polysulfide-sulfur transferase in Wolinella succinogenes.
The periplasmic Sud protein which is induced in Wolinella succinogenes growing by polysulfide respiration, has been previously proposed to serve as a polysulfide binding protein and to transfer polysulfide-sulfur to the active site of polysulfide reductase [Klimmek, O, Kreis, V., Klein, C., Simon, J., Wittershagen, A. & Kröger, A. (1998) Eur. J. Biochem. 253, 263-269.]. The results presented in this communication suggest that polysulfide-sulfur is covalently bound to the single cysteine residue (Cys109) of the Sud monomer, and that Cys109 is required for tight binding of polysulfide-sulfur and for sulfur transfer. A modified Sud protein [(C109S)Sud-His6] in which the cysteine residue was replaced by serine, did not catalyze sulfur transfer from polysulfide to cyanide and did not stimulate electron transport to polysulfide, in contrast to Sud-His6. The polysulfide-sulfur bound to (C109S)Sud-His6 was fully removed upon dialysis against sulfide. After this treatment, Sud-His6 retained one sulfur atom per monomer; thiocyanate was formed upon addition of cyanide to the preparation. After incubation of Sud-His6 with polysulfide, a proportion of the Sud-His6 monomers carried one or two sulfur atoms, as shown by matrix-assisted laser desorption ionization mass spectrometry. The sulfur atoms were absent from monomers derived from Sud-His6 treated with cyanide and from (C109S)Sud-His6 incubated with polysulfide.
Klimmek
O
O
Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany.
Stein
T
T
Pisa
R
R
Simon
J
J
Kröger
A
A
D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D020134:Catalytic Domain; D003545:Cysteine / Q000737:chemistry; D004579:Electron Transport; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D010088:Oxidoreductases / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013053:Spectrophotometry; D013440:Sulfides / Q000378:metabolism; D013466:Sulfurtransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016968:Wolinella / Q000201:enzymology* / Q000235:genetics
D001426:Bacterial Proteins; D013440:Sulfides; C032915:polysulfide; D010088:Oxidoreductases; C074883:polysulfide reductase; D013466:Sulfurtransferases; D003545:Cysteine