Dinucleotide-binding site of bovine liver catalase mimics a catalase mRNA-binding protein domain

Rat lung contains protein that interacts with catalase mRNA to form specific, redox-sensitive RNA-protein complexes. The studies in this report were aimed at determining whether catalase protein binds its own RNA. We found that rat catalase RNA binds NADPH-depleted bovine liver catalase (Sigma) but does not bind bovine liver catalase in the presence of NADPH. Complex formation between liver catalase and catalase RNA is competitively eliminated by a CA dinucleotide repeat. These data suggest the dinucleotide binding site of catalase mimics or is homologous to a catalase RNA-binding protein domain. These findings support the hypothesis that a class of RNA-binding proteins may have evolved from (di)nucleotide binding enzymes (M. W. Hentze. Trends Biol. Sci. 19: 101, 1994). When bovine liver catalase from two other commercial sources (Calbiochem and Boehringer) was used, we could not detect binding to catalase RNA. We have not yet been able to identify the basis for this difference. Thus the physiological importance of our observation of the NADPH-sensitive protein binding to catalase RNA cannot be assessed at this time.