THE MESSENGER-RNA-BINDING PROTEIN COLBP IS GLUTAMATE-DEHYDROGENASE

Expression of the liver-type isopeptides of cytochrome c oxidase is re gulated post-transcriptionally. An RNA-binding activity has been found in only those cells where the liver-type subunits are detected, This binding protein, termed COLBP, recognises sequences or structures with in the 3'-untranslated regions of transcripts encoding these liver-typ e isopeptides and has been implicated in the modulation of mRNA expres sion, We now show by subcellular fractionation, immunocompetition, UV- crosslinking and shift-Western studies that the metabolic enzyme gluta mate dehydrogenase, previously reported as being able to bind RNA, is the cytochrome c oxidase transcript-binding protein, COLBP.