title: S-nitrosothiols react preferentially with zinc thiolate clusters of metallothionein III through transnitrosation.
abstract: Metallothionein (MT) is a two-domain protein with zinc thiolate clusters that bind and release zinc depending on the redox states of the sulfur ligands. Since S-nitrosylation of cysteine is considered a prototypic cellular redox signaling mechanism, we here investigate the reactions of S-nitrosothiols with different isoforms of MT. MT-III is significantly more reactive than MT-I/II toward S-nitrosothiols, whereas the reactivity of all three isoforms toward reactive oxygen species is comparable. A cellular system, in which all three MTs are similarly effective in protecting rat embryonic cortical neurons in primary culture against hydrogen peroxide but where MT-III has a much more pronounced effect of protecting against S-nitrosothiols, confirms this finding. MT-III is the only isoform with consensus acid-base sequence motifs for S-nitrosylation in both domains. Studies with synthetic and zinc-reconstituted domain peptides demonstrate that S-nitrosothiols indeed release zinc from both the alpha- and the beta-domain of MT-III. S-Nitrosylation occurs via transnitrosation, a mechanism that differs fundamentally from that of previous studies of reactions of MT with NO*. Our data demonstrate that zinc thiolate bonds are targets of S-nitrosothiol signaling and further indicate that MT-III is biologically specific in converting NO signals to zinc signals. This could bear importantly on the physiological action of MT-III, whose biological activity as a neuronal growth inhibitory factor is unique, and for brain diseases that have been related to oxidative or nitrosative stress.
authors.affiliation: Center for Biochemical and Biophysical Sciences and Medicine, Harvard Medical School, One Kendall Square, Building 600, Cambridge, Massachusetts 02139, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Irie
authors.forename: Wing Ming
authors.initials: WM
authors.lastname: Keung
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Maret
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D006801:Humans; D006861:Hydrogen Peroxide / Q000493:pharmacokinetics; D007700:Kinetics; D008668:Metallothionein / Q000378:metabolism*; D000090023:Metallothionein 3; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009498:Neurotoxins / Q000633:toxicity; D009603:Nitroso Compounds / Q000493:pharmacokinetics* / Q000494:pharmacology; D011817:Rabbits; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013438:Sulfhydryl Compounds / Q000493:pharmacokinetics* / Q000494:pharmacology; D015032:Zinc / Q000378:metabolism*
chemical_list: D000090023:Metallothionein 3; D009419:Nerve Tissue Proteins; D009498:Neurotoxins; D009603:Nitroso Compounds; D013438:Sulfhydryl Compounds; D008668:Metallothionein; D006861:Hydrogen Peroxide; D015032:Zinc