Cloning and Characterization of a Tyrosine Aminotransferase( TAT)Gene in Gerbera hybrida

In our previous study,a gene predicted to encode a Tyrosine aminotransferase( TAT) was found to be significantly up-regulated in root rot diseased Gerbera by transcriptome sequencing. To confirm the genes and investigate the function,we cloned the gene by RT-PCR and then conduct bioinformatic analyses. In this study,a 1 537 bp long c DNA sequence of this gene( named as Gh TAT) was firstly cloned,which contained a coding region of 1 233 bp,which was predicted to encode a protein of 410 amino acids. Bioinformatic analysis showed that the Gh TAT was a stable hydrophobic protein without signal peptide. Subcellular location prediction result indicated that this protein located in chloroplast,which is the biosynthesis position of tyrosine and the derived products of tyrosine biosynthesis pathway. Moreover,typical Tyrosine aminotransferase domain was found in this protein,indicating that it is a TAT. According to the TAT-based phylogenetic analysis and similarity analysis,the closest relationship and highest similarity was found between Gh TAT and Halianthus annuus TAT,which again verified the TAT property of Gh TAT. Tyrosine aminotransferase( TAT) is the first enzyme in tyrosine biosynthesis pathway,whose products include many antioxidant substances such as tocopherols and tocotrienols. The up-regulation of Gh TAT in root rot diseased gerbera suggests that it may play an important role in response to the root rot pathogen infection. In addition,60 phosphorylation sites( accounting for 14. 6%) were found in this protein,suggesting that the expression of this protein and its encoding gene were greatly influenced by the phosphorylation reactions.

Tyrosine Aminotransferase Gene (SmTAT) Revealed Genetic Diversity and Phylogeny of Cultivated Danshen (Salvia miltiorrhiza) Populations

Chinese traditional medicine Danshen is the radix of the perennial herbs of Salvia miltiorrhiza Bunge, which has a variety of pharmacological effects and is traditionally and extensively applied clinically to treat cardiovascular disorders. In this research, the genomic genes for tyrosine aminotransferase (TAT) of 38 cultivated populations of Danshen in China were cloned and bioinformatic analyses were conducted to reveal its genetic diversity and phylogeny. The full-length SmTAT was 2296 - 2444 bp including 6 exons (encoding 411 amino acids) and 5 introns. Overall, the SmTAT genes in cultivated Danshen populations are highly conserved with a relative low level of genetic diversity. The spliced exons (1236 bp) had 23 SNP variations with a rate of 1.86%, of which 22 occurred in the white flower S. miltiorrhiza Bge.f.alba population (W-SCHY-W-1) and led to 5 amino acid variations. The entire 290 SNP variations with a rate of 24% in the 5 introns occurred exclusively in W-SCHY-W-1. Phylogenetic trees based on the full-length, combined introns, the spliced exons, and the deduced amino acid sequences of SmTAT all showed a two-clade basic structure with W-SCHY-W-1 uniquely standing alone. The SmTAT gene of the white flower population (W-SCHY-W-1) is unique and especially rich in variations. The first time clarified genomic SmTAT gene structure and genetic diversity in cultivated Danshen populations laid an excellent foundation for further studies on the biosynthesis of bioactives and the molecular breeding of Danshen as well as in plant tyrosine metabolism.

Tyrosine aminotransferase: biochemical and structural properties and molecular dynamics simulations

Tyrosine aminotransferase(TAT)catalyzes the transamination of tyrosine and other aromatic amino acids.The enzyme is thought to play a role in tyrosinemia type II,hepatitis and hepatic carcinoma recovery.The objective of this study is to investigate its biochemical and structural characteristics and substrate specificity in order to provide insight regarding its involvement in these diseases.Mouse TAT(mTAT)was cloned from a mouse cDNA library,and its recombinant protein was produced using Escherichia coli cells and purified using various chromatographic techniques.The recombinant mTAT is able to catalyze the transamination of tyrosine usingα-ketoglutaric acid as an amino group acceptor at neutral pH.The enzyme also can use glutamate and phenylalanine as amino group donors and p-hydroxyphenylpyruvate,phenylpyruvate and alpha-ketocaproic acid as amino group acceptors.Through macromolecular crystallography we have determined the mTAT crystal structure at 2.9Åresolution.The crystal structure revealed the interaction between the pyridoxal-5′-phosphate cofactor and the enzyme,as well as the formation of a disulphide bond.The detection of disulphide bond provides some rational explanation regarding previously observed TAT inactivation under oxidative conditions and reactivation of the inactive TAT in the presence of a reducing agent.Molecular dynamics simulations using the crystal structures of Trypanosoma cruzi TAT and human TAT provided further insight regarding the substrate-enzyme interactions and substrate specificity.The biochemical and structural properties of TAT and the binding of its cofactor and the substrate may help in elucidation of the mechanism of TAT inhibition and activation.