The 2-oxoglutarate dehydrogenase complex from Azotobacter vinelandii. 1. Molecular cloning and sequence analysis of the gene encoding the 2-oxoglutarate dehydrogenase component.

The nucleotide sequence of the gene encoding the 2-oxoglutarate dehydrogenase component (E1o) of the 2-oxoglutarate dehydrogenase complex from Azotobacter vinelandii has been determined. The protein-coding sequence consists of 2832 bp (944 codons, including the AUG start codon and the UAA stop codon). The predicted molecular mass (105,687 Da) is in good agreement with that published for the isolated enzyme. The E1o gene is separated from the gene encoding the E2o component by a 42-bp intergenic region. No Escherichia-coli-like promoter sequences are found in the sequenced 97 bp upstream from the E1o gene. A putative ribosome-binding site is located 10-16 bp upstream from the start codon of the E1o gene. No terminator sequences could be detected downstream from the stop codon. Together with the identical situation for the E2o gene and the presence of terminating sequences downstream of the E3 gene, it can be assumed that all three genes of the 2-oxoglutarate dehydrogenase multienzyme complex are transcribed as a single mRNA transcript under the control of a promoter, located more than 100 bp upstream of the E1o gene, analogous to the pyruvate dehydrogenase complex in E. coli. The similarity with the sucA gene of E. coli is high with 59% identity.