%0 Journal Article
%T Molecular cloning and characterization of Escherichia coli K12 ygjG gene
%A Natalya N Samsonova
%A Sergey V Smirnov
%A Irina B Altman
%A Leonid R Ptitsyn
%J BMC Microbiology
%D 2003
%I BioMed Central
%R 10.1186/1471-2180-3-2
%X The 1.8-kbp DNA fragment containing E. coli K12 ygjG gene with aer-ygjG intergenic region was examined. It was found that the fragment contains ¦Ò54-depended open reading frame (ORF) of 1,380 nucleotides encoding a 459-amino acid polypeptide of approximately 49.6 kDa. The cytidine (C) residue localized 10 bp downstream of the ¦Ò54 promoter sequence was identified as the first mRNA base. The UUG translation initiation codon is situated 36 nucleotides downstream of the mRNA start. The YgjG was expressed as a his6-tag fused protein and purified to homogeneity. The protein catalyzed putrescine:2-oxoglutaric acid (2-OG) aminotransferase reaction (PATase, EC 2.6.1.29). The Km values for putrescine and 2-OG were found to be 9.2 mM and 19.0 mM, respectively. The recombinant enzyme also was able to transaminate cadaverine and, in lower extent, spermidine, and gave maximum activity at pH 9.0.Expression of E. coli K12 ygjG coding region revealed ¦Ò54-depended ORF which encodes a 459-amino acid protein with putrescine:2-OG aminotransferase activity. The enzyme also was able to transaminate cadaverine and, in lower extent, spermidine.Polyamines, such as putrescine and spermidine, are present in virtually all living cells, from bacteria to plant and human cells, with a very important though poorly understood biological role [1,2]. They can bind to nucleic acids, stabilize membrane and stimulate activity of several enzymes [2-5]. Despite the proved necessity of intracellular polyamine for optimal cellular growth, polyamine accumulation can lead to inhibition of cellular growth and protein synthesis [6,7]. Two major metabolic routes of polyamines breakdown have been described, one for the free bases via ¦¤1-pyrroline (4-aminobutyraldehyde) and the other via N-acetyl derivatives. Acetylation pathway serves to prevent polyamine toxicity in prokaryotes and eukaryotes [1,8]. Spermidine and spermine are acetylated and further oxidized by polyamine oxidase or either deacetylated or excreted
%U http://www.biomedcentral.com/1471-2180/3/2