Nucleotide sequence of the lipoamide dehydrogenase gene of Escherichia coli K12

Abstract

The nucleotide sequence of a 1980-base-pair segment or DNA, containing the lpd gene encoding the lipoamide dehydrogenase component (E3) of the pyruvate dehydrogenase complex of Escherichia coli K 12, has been determined by the dideoxy chain-termination method. The Ipd structural gene comprises 1419 base pairs (473 codons, excluding the initiating AUG codon). It is preceded by a good promoter and an excellent ribosome binding site and it ends with a typical rho-independent terminator sequence. The results confirm that the lpd gene is an independent gene linked to, but not part of, the ace operon that encodes the E l and E2 components of the pyruvate dehydrogenase complex. The location and transcriptional polarity of the lpd gene relative to the restriction map of the corresponding region of DNA, are completely consistent with previous genetic and post-infection labelling studies. The composition, M , (50554 or 51 274 if the F A D cofactor is included), aminoterminal sequence and carboxy-terminal sequence predicted from the nucleotide sequence are in excellent agreement with previous studies on the purified enzyme. The enzyme also exhibits a remarkable degree of sequence homology with peptides of the pig heart enzyme and with other pyridine nucleotide disulphide oxidoreductases whose sequences have been defined : human erythrocyte glutathione reductase and plasmid-encoded mercuric reductase.Lipoamide dehydrngenase is the flavoprotein component (E3) of the pyruvate and 2-oxoglutarate dehydrogenase multienzyme complexes [I -31. These complexes catalyse the oxidative decarboxylation of pyruvate and 2-oxoglutarate with the formation of acetyl-CoA and succinyl-CoA, respectively :In Escheridzia coif the complexes contain multiple copies of three types of subunit: the pyruvate or 2-oxoglutaratc dehydrogenase (El), the dihydrolipoamide acetyltransferase or succinyltransferase (E2) and lipoamide dehydrogenase (E3). The lipoamide dehydrogenase component is a dimer containing identical subunits of M , = 52000-59000 [4-71. It catalyses the reoxidation of the dihydrolipoyl groups bound by amide linkage to lysine residues or the acyltransferases. These groups are reduced during the oxidative decarboxylation of 2-ox0 acids to acyl-CoA, and their reoxidation enables the cycle of reactions to continue:where TPP is thiamin pyrophosphate. Lipoamide dehydrogenases have been isolated from many sources, both prokaryotic and eukaryotic : they are remarkably resistant to heat inactivation and proteolysis, and they each contain a flavin (FAD) coenzyme and an active disulphide bond. They belong to a family of pyridine nucleotide oxidoreductases that includes glutathione reductase and thioredoxin reductase [3].In E. coli genetic studies with mutants deficient in lipoamide dehydrogenase have established that the E3 components of the pyruvate and 2-oxoglutarate complexes are encoded by a single gene, lpd [8 -lo]. This confirmed earlier findings that the E3 components of the two complexes are identical with respect to various physical, en7ymat...

Cloning and sequence analysis of the genes encoding the dihydrolipoamide acetyltransferase and dihydrolipoamide dehydrogenase components of the pyruvate dehydrogenase multienzyme complex of Bacillus stearothermophilus

“…2). This is in contrast with the 324-bp intergenic space between the uceF and Ipd genes for the E2 and E3 chains in E. coli [57]. In the latter organism, there is a terminator following the aceF gene and the Ipd gene can be transcribed from its own promoter.…”

Secretory S complex of Bacillus subtilis: sequence analysis and identity to pyruvate dehydrogenase

“…This redistribution supported the concept that MBRP participates in secretion. Moreover, antiserum to the S. aureus 60-kDa protein immunoprecipitated from B. subtilis cell lysate a set of four proteins of 43,40,64, and 62 kDa (1). The molecular weights of these proteins are similar enough to those of the B. subtilis S complex to indicate that the antiserum directed against the S. aureus MBRP complex recognizes the B. subtilis S complex.…”

Antibodies against an inter‐domain segment of polypeptide chain inhibit active‐site coupling in the pyruvate dehydrogenase multienzyme complex

“…50-residue) domain responsible, at least in part, for binding the E3 subunits [4,5]. The inter-domain segments (PEP1-3) of the polypeptide chain are long (20-30-residue) sequences rich in alanine, pro-line and charged amino acids [2,3]. The E3-binding domain is in turn linked by a shorter and less conspicuously (alanine+proline)-rich segment to a large (approx.…”

“…The N-terminal half of the E2p chain contains a succession of three highly homologous lipoyl domains each of about 80 amino acids [2,3]; these are linked to each other and then to a smaller (approx. 50-residue) domain responsible, at least in part, for binding the E3 subunits [4,5].…”