Flexibility in proteins: tuning the sensitivity to O2 diffusion by varying the lifetime of a phosphorescent sensor in horseradish peroxidase.

The heme in horseradish peroxidase (HRP) was replaced by phosphorescent Pt-mesoporphyrin IX (PtMP), which acted as a phosphorescent marker of oxygen quenching and allowed comparison with another probe, Pd-mesoporphyrin IX (Khajehpour et al. (2003) Proteins 53, 656-666). Benzohydroxamic acid (BHA), a competitive inhibitor of the enzyme, was also used to monitor its effects on phosphorescence quenching.

Further study on S-nitrosation by nitrite.

At neutral pH, S-nitrosoglutathione was formed by the reaction of reduced glutathione and sodium nitrite. The degradation of S-nitrosoglutathione, presumably by transnitrosation/denitrosation, was catalyzed by L-cysteine, or CoA-SH. Additionally, from the crude extract of rat brain, one protein with a large molecular mass was nitrosolated with nitrite, and was split into duplet peptides noted in Western blot.

Nitrosation of cysteine and reduced glutathione by nitrite at physiological pH.

Unlike the formation of nitrosothiols by nitrous acid, our study revealed that NO2- effectively reacted with L-cysteine or reduced glutathione (GSH) at pH 7.0 and 7.4, to form orange-pink products of S-nitrosocysteine (CySNO) or S-nitrosoglutathione (GSNO).