S-nitrosation of serum albumin by dinitrosyl-iron complex.
The objective of this study was to identify a potential mechanism for S-nitrosation of proteins. Therefore, we assessed S-nitrosation of bovine serum albumin by dinitrosyl-iron-di-L-cysteine complex [(NO)2Fe(L-cysteine)2], a compound similar to naturally occurring iron-nitrosyls. Within 5-10 min, (NO)2Fe(L-cysteine)2 generated paramagnetic albumin-bound dinitrosyl-iron complex and S-nitrosoalbumin in a ratio of 4:1. Although S-nitroso-L-cysteine was concomitantly formed in low amounts, its concentration was not sufficient to account for formation of S-nitrosoalbumin via a trans-S-nitrosation reaction. Low oxygen tension did not affect S-nitrosation by the dinitrosyl-iron complex thus excluding the involvement of oxygenated NOx-species in the nitrosation reaction. Blockade of albumin histidine residues by pyrocarbonate, which prevented formation of dinitrosyl-iron-albumin complex, did not inhibit S-nitrosation of albumin. Thus, S-nitrosation of albumin by (NO)2Fe(L-cysteine)2 can proceed by direct attack of a nitrosyl moiety on the protein thiolate, without previous binding of the iron. We conclude that protein-bound dinitrosyl-iron complexes detected in high concentrations in certain tissues provide a reservoir of S-nitrosating species, e.g. low molecular dinitrosyl iron complexes.
D000818:Animals; D002417:Cattle; D003545:Cysteine / Q000031:analogs & derivatives* / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology; D012710:Serum Albumin, Bovine / Q000378:metabolism*
C072081:dinitrosyl-iron(II)-cysteine; D012710:Serum Albumin, Bovine; D003545:Cysteine; D010100:Oxygen