title: Characterization of a gene encoding dihydrolipoamide dehydrogenase of the cyanobacterium Synechocystis sp. strain PCC 6803.
abstract: The authors previously reported the isolation and partial characterization of a periplasmically located dihydrolipoamide dehydrogenase (LPD) from the cyanobacterium Synechocystis sp. strain PCC 6803. In the present work the gene (lpdA; database accession number Z48564) encoding the apoprotein of this LPD in Synechocystis PCC 6803 has been identified, sequenced and analysed. The lpdA gene codes for a protein starting with methionine, which is post-translationally removed. The mature protein contains an N-terminal serine and consists of 473 amino acids with a deduced molecular mass of 51421 Da (including one FAD). The LPD is an acidic protein with a calculated isoelectric point of 5.17. Comparison of the amino acid sequence of the Synechocystis LPD with protein sequences in the databases revealed that the enzyme shares identities of 31-35% with all 18 LPDs so far sequenced and published. As a first step in determining the role of this cyanobacterial LPD, attempts were made to generate an LPD-free Synechocystis mutant by insertionally inactivating the lpdA gene with a kanamycin-resistance cassette. However, the selected transformants appeared to be heteroallelic, containing both the intact lpdA gene and the lpdA gene inactivated by the drug-resistance cassette. The heteroallelic mutant studied, which had about 50% of the wild-type LPD activity, caused acidification of the growth medium. Growth over a prolonged time was only possible after an increased buffering of the medium. Since it is reported in the literature that inactivation of the pyruvate dehydrogenase complex (PDC) leads to acidosis, a function of the LPD in a cytoplasmic-membrane-associated PDC is conceivable.
authors.forename: Anke
authors.initials: A
authors.lastname: Engels
authors.affiliation: Universitt Bielefeld, Biologie VIII: Zellphysiologie,33501 Bielefeld,Germany.
authors.forename: Elfriede K
authors.initials: EK
authors.lastname: Pistorius
mesh_terms: D000595:Amino Acid Sequence; D001059:Apoproteins / Q000235:genetics; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000201:enzymology / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D008058:Dihydrolipoamide Dehydrogenase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D018628:Gene Dosage; D005798:Genes, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016254:Mutagenesis, Insertional; D016366:Open Reading Frames; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D001059:Apoproteins; D004269:DNA, Bacterial; D011993:Recombinant Fusion Proteins; D008058:Dihydrolipoamide Dehydrogenase