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Nearly full length cDNA clones encoding the pyruvate dehydrogenase (PDH) E1α subunit of adult human brain and liver were isolated, sequenced, and compared to other clones reported recently. Both of our clones have identical sequences except one bp, and contain the entire protein coding region of pyruvate dehydrogenase E1α subunit. The proteins of pyruvate dehydrogenase E1α subunit deduced from the cDNA sequences have 390 and 361 amino acids with molecular masses of 43,301 and 40,234 daltons for the immature and the mature protein, respectively. Although nucleotide sequences of our cDNA clones are highly homologous (more than 99%) to those of other cDNA clones for PDH E1α isolated from human fetal liver, hepatoma, and foreskin, the deduced protein structures differ greatly. The deduced protein sequences of our clones are highly homologous with the protein deduced from the hepatoma clone except two amino acid residues at 349 and 354. The protein deduced from the fetal liver cDNA clone has two frameshifts at amino acid positions 106 and 174. The protein deduced from the human foreskin cDNA has a deletion at nucleotide 317 and insertions of T at nucleotide 405-406 and of G at nucleotide 510-511, resulting in different PDH E1α protein structures. The identical amino acid sequences of the brain and liver proteins indicate that the pyruvate dehydrogenase E,u subunits in two different tissues do not represent different isozymes and that they are probably derived from an identical gene.
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