Cloning and sequencing of the genes of 2-hydoxyglutaryl-CoA dehydratase from Acidaminococcus fermentans.

Two genomic libraries from Acidaminococcus fermentans DNA constructed with the lambda vectors gt11 and EMBL 3 were screened with antisera raised against 2-hydroxyglutaryl-CoA dehydratase. Two clones giving the strongest reaction in the immunoassay were analyzed further, one was a lambda gt11 clone with an insert of 2050 bp and one was a lambda EMBL-3 clone with an insert of approximately 11,000 bp. Escherichia coli cells infected with the lambda gt11 clone expressed the alpha subunit of the dehydratase (Mr, 53,870), whereas with the lambda EMBL-3 clone, the alpha and beta subunits (Mr, 41,857) were detected on Western blots. Restriction fragments of both clones were subcloned in pUC 8 and sequenced by the chain termination method. Thus the complete sequence of the genes of both subunits, hgdA (alpha) and hgdB (beta) were obtained. The genes have the following order: A-B, with an intergenic region of only 2 bp. The deduced amino acid sequences for the alpha and beta subunits were confirmed by four peptides sequenced by protein chemical methods. Both chains are extremely rich in cysteine (13 in alpha, including a CNC and two CC clusters, and nine in beta) but no similarities to other known protein sequences were found.