Stress-related genes heat shock proteins

Hemeoxygenase-1 (HOI) and hemeoxygenase-2 (H02), members of the stress protein superfamily, are deployed in the ER. Three HO isoforms (HOI, H02, and H03) have been identified. HOI is a 32 kDa heat-shock protein with a low expression in brain that increases after heat shock. H02 is a constitutively synthesized 36 kDa protein that has its major activity in the brain (Trakshel et al., 1988). H03 is related to H02 but is the product of a different gene. They catalyze the oxidative degradation of pro-oxidant metalloporphyrins such as heme (potential pro-oxidant) to biliverdin, which is subsequently converted to bilirubin (potential antioxidant) by biliverdin reductase and carbon monoxide, finally releasing iron (pro-oxidant Ewing andMaines, 1991). 

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