An aspartate aminotransferase from an extremely thermophilic bacterium, Thermus thermophilus HB8. 1996

A Okamoto, and R Kato, and R Masui, and A Yamagishi, and T Oshima, and S Kuramitsu
Department of Biology, Faculty of Science, Osaka University, Toyonaka.

The aspartate aminotransferase gene (AspAT, EC 2.6.1.1) of an extremely thermophilic bacterium, Thermus thermophilus HB8, was cloned and sequenced, and its gene product was overproduced. The purified T. thermophilus AspAT was stable up to about 80 degrees C at neutral pH. T. thermophilus AspAT was strictly specific for acidic amino acid substrates, such as aspartate, glutamate, and the respective keto acids. The gene coding for T. thermophilus AspAT showed that it comprised 1,155 bp with a high G+C content (70 mol%), and encoded a 385-residue protein with a molecular weight of 42,050. The amino acid sequence of T. thermophilus AspAT deduced from its gene showed about 15, 46, and 29% homology with those from Escherichia coli, Bacillus sp. YM-2, and Sulfolobus solfataricus, respectively. When the amino acid sequence of T. thermophilus AspAT was compared with that of E. coli AspAT, the number of Cys was found to have decreased from 5 to 1, that of Asn from 23 to 9, that of Gln from 16 to 8, and that of Asp from 20 to 13, all of which are known to be relatively labile at high temperatures. Conversely, the number of Pro was increased from 15 to 25, Arg from 22 to 32, and Glu 27 to 37. As shown by the E. coli AspAT structure, there was a marked tendency for the extra prolyl residues to be located around the surface of the molecule. This was quite different from that in the case of RecA protein, which shows an increased number of prolyl residues in the interior of its molecule. Different strategies of different proteins as to prolyl contribution to thermostability have been suggested. Despite the high degree of conservation of active-site residues, Arg292 in E. coli AspAT, which interacts with the distal carboxylate of the substrate, was not found in T. thermophilus AspAT. Arg89 may complement the function of Arg292.

UI MeSH Term Description Entries
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D011487 Protein Conformation The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain). Conformation, Protein,Conformations, Protein,Protein Conformations
D011732 Pyridoxal Phosphate This is the active form of VITAMIN B 6 serving as a coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids, aminolevulinic acid. During transamination of amino acids, pyridoxal phosphate is transiently converted into pyridoxamine phosphate (PYRIDOXAMINE). Pyridoxal 5-Phosphate,Pyridoxal-P,Phosphate, Pyridoxal,Pyridoxal 5 Phosphate,Pyridoxal P
D002942 Circular Dichroism A change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Circular Dichroism, Vibrational,Dichroism, Circular,Vibrational Circular Dichroism
D003001 Cloning, Molecular The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells. Molecular Cloning
D004926 Escherichia coli A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc. Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D006358 Hot Temperature Presence of warmth or heat or a temperature notably higher than an accustomed norm. Heat,Hot Temperatures,Temperature, Hot,Temperatures, Hot
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D001219 Aspartate Aminotransferases Enzymes of the transferase class that catalyze the conversion of L-aspartate and 2-ketoglutarate to oxaloacetate and L-glutamate. EC 2.6.1.1. Aspartate Aminotransferase,Aspartate Transaminase,Glutamic-Oxaloacetic Transaminase,SGOT,Aspartate Apoaminotransferase,Glutamate-Aspartate Transaminase,L-Aspartate-2-Oxoglutarate Aminotransferase,Serum Glutamic-Oxaloacetic Transaminase,Aminotransferase, Aspartate,Aminotransferase, L-Aspartate-2-Oxoglutarate,Aminotransferases, Aspartate,Apoaminotransferase, Aspartate,Glutamate Aspartate Transaminase,Glutamic Oxaloacetic Transaminase,Glutamic-Oxaloacetic Transaminase, Serum,L Aspartate 2 Oxoglutarate Aminotransferase,Serum Glutamic Oxaloacetic Transaminase,Transaminase, Aspartate,Transaminase, Glutamate-Aspartate,Transaminase, Glutamic-Oxaloacetic,Transaminase, Serum Glutamic-Oxaloacetic

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