MOLECULAR-CLONING AND ANALYSIS OF THE EXPRESSION OF THE E1-BETA SUBUNIT OF BRANCHED-CHAIN ALPHA-KETOACID DEHYDROGENASE IN MICE

The cDNA sequence encoding the murine liver E1 beta subunit of the bra nched-chain alpha-ketoacid dehydrogenase complex (BCKAD) was determine d. In the region encoding the mature E1 beta subunit protein, both the nucleotide composition and predicted amino acid sequence are highly c onserved between murine, rat, human, and bovine species. In contrast, they are less well conserved in the 5' sequence encoding the amino ter minal preprotein sequence and 3' untranslated region. The pattern of t issue-specific expression of three BCKAD subunit RNAs was determined t o be similar in both rat and murine tissues except for that observed i n murine liver, where a higher than expected level of E1 beta subunit RNA was observed. Variation in the levels of this subunit might play a major role in the regulation of the overall ability of the murine liv er to modulate BCKAD content in response to changing physiologic needs .