Iron Regulatory Protein-1 RNA-Binding Activity

Iron regulatory protein (IRP)-l RNA-binding activity was induced by nitric oxide (Drapier et al. 1993, Weiss et al. 1993). Activation in cells required a time of treatment similar to desferrioxamine, and while it remains possible that NO indirectly induces IRP-1 via modulation of intracellular iron levels, the in vitro analysis of recombinant IRP-1 suggested that NO can direct affect the [Fe-S] cluster (Drapier et al. 1993). 

When prepared in the presence of oxygen, IRP-1 contains both the [3Fe-4S] and the [4Fe-4S] forms (2000 to 5000 nmol of c/s-aconitate/min x mg protein) (Soum et al. 2000). When exposed to nitric oxide generated by 3-morpholino-sydnonimine (SIN-1) in the presence of superoxide dismutase for 2 h at 37 °C, IRP-1 lost about 80% of its aconitase activity and its iron responsive element-binding capacity was increased 3- to 5-fold when further ex- 

Addition of a metal ion to a [3Fe-4S] cuboidal cluster to yield a [4Fe-4S] cubane [80] 

Catalase (EC 1.11.1.6) rapidly formed a reversible complex stoichiometrically with nitric oxide with the Soret band shifting from 406 to 426 nm and two new peaks appeared at 540 and at 575 nm, consistent with the formation of a ferrous-nitrosyl complex (Brunelli et al. 2001). Catalase consumed more nitric oxide upon the addition of hydrogen peroxide. Conversely, micromolar concentrations of nitric oxide slowed the catalase-mediated decomposition of hydrogen peroxide. Catalase pre-treated with nitric oxide and hydrogen peroxide regained full activity after dialysis. 

In the isolated perfused lungs of Sprague-Dawley rats given silica (50 mg) intratracheally, nitrate production as an index of NO production, was significantly greater (53.5 12.0 nmol/90 min) compared 

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