Cloning and mutagenesis of the rabbit ApoB mRNA editing protein. A zinc motif is essential for catalytic activity, and noncatalytic auxiliary factor(s) of the editing complex are widely distributed.

摘要: Apolipoprotein (apo) B mRNA editing is the specific deamination of cytidine (nucleotide 6666) to uridine in apoB mRNA. We isolated a full-length cDNA clone encoding rabbit protein (REPR), subunit complex. Rabbit REPR analogous rat enterocyte 27-kDa that has been shown have deaminase activity. Like REPR, edited synthetic RNA when mixed with chicken extract. Surprisingly, also acquired activity extracts from various organs (liver, gallbladder, stomach, intestine, adrenals, thyroid, testes, spleen, kidney, and lung) or (kidney liver). In contrast, was found only small large intestine. Thus, auxiliary protein(s) complex, which are essential for activity, exist devoid significant synthesis. requires zinc its catalytic mutated putative zinc-coordinating residues (His61, Cys93, Cys96) 2 additional (Glu63, Pro92) conserved other deoxycytidylate deaminases REPR. The wild-type mutant cDNAs each produced 28-kDa proteins transcribed translated vitro. Compared mutations His61-->Ala, Glu63-->Ala, Cys93-->Ala, Cys96-->Ala abolished greatly reduced whereas His61-->Cys (which can coordinate zinc) Pro92-->Ala had lesser effect. These results indicate His61, Cys96 probably because they zinc, Glu63 essential, it may be involved reaction. addition, widespread distribution factor(s) portends their involvement reactions.