Dihydrolipoamide dehydrogenase from Haloferax volcanii: gene cloning, complete primary structure, and comparison to other dihydrolipoamide dehydrogenases

Abstract

We used the N-terminal amino acid sequence of dihydrolipoamide dehydrogenase from Haloferax volcanii, to design and synthesize two oligonucleotide probes that were used to identify and clone a 4.3 kilobase pair (kbp) fragment from MboI restriction endonuclease digestion of Hf. volcanii genomic DNA. The nucleotide sequence of a 1.5-kbp region of this clone was determined and this revealed an open reading frame that translated into a protein with good homology to dihydrolipoamide dehydrogenase from other sources. The first 48 amino acids were identical with the N-terminal sequence data obtained from the purified protein. The complete primary structure of the halophilic dihydrolipoamide dehydrogenase was analyzed in terms of its homologies to dihydrolipoamide dehydrogenases from other sources and its molecular adaptations to high intracellular ionic strength.Key words: Archaea, halophile, flavoenzyme, nucleotide sequence.