To study the expression of a ferredoxin gene in extra-adrenocortical tissues, the amounts and structures of the ferredoxin gene transcripts in bovine liver and brain were studied and compared to those of that in adrenocortex. 2. The sizes and amounts of the ferredoxin mRNAs were analyzed by means of Northern blotting, RNA slot blotting and RT-PCR. 3. The nucleotide sequences were determined for 39 ferredoxin cDNA clones from bovine liver. 4. The results indicated that the sizes of the ferredoxin mRNAs in liver and brain were the same as that in adrenocortex, however, their amounts were approx 1/30th and less than the latter, respectively. 5. Although the multiple forms of ferredoxin cDNA, differing in the poly(A) addition sites, were also found in liver, a minor form of ferredoxin cDNA, produced through alternative promoter usage and splicing, could not be detected in liver. 6. The nucleotide sequences of all hepato-ferredoxin cDNA clones obtained were identical to that of a major type of adreno-ferredoxin. 7. These results showed that the expression level of the ferredoxin gene in different tissues was controlled by the amount of mRNA.
