Cloning and sequence analysis of the genes encoding the α and β subunits of the E1 component of the pyruvate dehydrogenase multienzyme complex of Bacillus stearothermophilus

Abstract

A 4175‐bp EcoRI fragment of DNA that encodes the α and β chains of the pyruvate dehydrogenase (lipoamide) component (E1) of the pyruvate dehydrogenase multienzyme complex of Bacillus stearothermophilus has been cloned in Escherichia coli. Its nucleotide sequence was determined. Open reading frames (pdhA, pdhB) corresponding to the E1α subunit (368 amino acids, Mr 41312, without the initiating methionine residue) and E1β subunit (324 amino acids, Mr 35306, without the initiating methionine residue) were identified and confirmed with the aid of amino acid sequences determined directly from the purified polypeptide chains. The E1β gene begins just 3 bp downstream from the E1a stop codon. It is followed, after a longer gap of 73 bp, by the start of another but incomplete open reading frame that, on the basis of its known amino acid sequence, encodes the dihydrolipoyl acetyltransferase (E2) component of the complex. All three genes are preceded by potential ribosome‐binding sites and the gene cluster is located immediately downstream from a region of DNA showing numerous possible promoter sequences. The E1α and E1β subunits of the B. stearothermophilus pyruvate dehydrogenase complex exhibit substantial sequence similarity with the E1α and E1β subunits of pyruvate and branched‐chain 2‐oxo‐acid dehydrogenase complexes from mammalian mitochondria and Pseudomonas putida. In particular, the E1α chain contains the highly conserved sequence motif that has been found in all enzymes utilizing thiamin diphosphate as cofactor. Copyright © 1990, Wiley Blackwell. All rights reserved