Isolation and functional characterization of a cyst(e)amine-sensitive protein protecting methyl-dithio groups

• Published in: Biochimie 2004-12, Vol.86 (12), p.951-961
• Main Authors: Jókay, István, Kelemenics, Katalin, Patthy, András, Bali, László, Bátkai, László
• Format: Article
• Language: English
• Subjects: 2-Mercaptoethanol; Animals; Anti-methyl(di)thio factor; Assay for methylthio disulfides; Cyst(e)amine; Cystamine - pharmacology; Dimethyl Sulfoxide - pharmacology; Dimethylsulfoxide; Disulfides - chemistry; Liver - chemistry; Mercaptoethanol - pharmacology; Methane - analogs & derivatives; Methane - chemistry; Mice; Molecular Weight; Photometry - methods; Proteins - chemistry; Proteins - isolation & purification; S-methylthio-cysteine; Sulfhydryl Compounds - metabolism
• ISSN: 0300-9084; 1638-6183
• DOI: 10.1016/j.biochi.2004.07.015

We have previously shown that S-methylthio cysteine mixed disulfide and cystamine potently stimulate thiol production and glutathione synthesis of a human T-cell line in SH-poor medium. Here, we describe a simple photometric method for the determination of methylthio-mixed disulfides (MT-groups) and show that liver contains relatively large amount of MT-groups mainly associated with the globulin fractions. At least a part of methylthio (MT-) globulins is in a complex with a heat-stable protein protecting methylthio-groups against reduction and was designated as anti-methylthio factor (AMTF). Similar complexes are present in some animal sera. AMTF isolated from mouse liver was shown to specifically inhibit redox interaction of methyldithio-groups of various origin with thiols but loses this ability in the presence of some agents such as cyst(e)amine, 2-mercaptoethanol and dimethyl sulfoxide abrogating the MT-binding activity of AMTF (= cystamine-sensitive protein—CSP). AMTF purified by heat treatment and isopropanol fractionation was chromatographed on Superose-12 column. Preliminary results showed that the molecular mass of the active component is about 34 kDa consisting of two identical subunits. The possible biological role of MT–AMT complexes was discussed.