Molecular biology synthetase

As any elementary textbook on molecular biology will relate, the sequences of proteins are stored in DNA in the form of a triplet code. Each amino acid is encoded by one or more triplet combinations of the four bases A, T, G, and C. For example, tryptophan is coded by the sequence TGG. The sequence of triplets is converted into a protein by a process in which DNA is first transcribed into mRNA. This message is then translated into protein on the ribosomes in conjunction with tRNA and the aminoacyl-tRNA synthetases. In prokaryotes, there is a one-to-one relationship between the sequence of triplets in the DNA. and the sequence of amino acids in the protein. In eukaryotes, the DNA often contains stretches of intervening sequences or introns which are excised from the mRNA after transcription (Chapter 1). 

Bennett, M.J., Lightfoot, D.A. Cullimore, J.V. (1989). cDNA sequence and differential expression of the gene encoding the glutamine synthetase y polypeptide of Phaseolus vulgaris L. Plant Molecular Biology 12, 553-65. 

Cock, J.M., Brock, I.W., Watson, A.T., Swarup, R., Morby, A.P. Cullimore, J.V. (1991). Regulation of glutamine synthetase genes in leaves of Phaseolus vulgaris. Plant Molecular Biology 17, 761-71. 

Cock, J.M., Mould, R.M., Bennett, M.J. Cullimore, J.V. (1990). Expression of glutamine synthetase genes in roots and nodules of Phaseolus vulgaris following changes in the ammonium supply and infection with various Rhizobium mutants. Plant Molecular Biology 14, 549-60. 

Forde, B.G. Cullimore, J.V. (1989). The molecular biology of glutamine synthetase in higher plants. In Oxford Surveys of Plant Molecular and Cell Biology, vol. 6, ed. B.J. Miflin, pp. 247-96. Oxford Oxford University Press. 

Sakamoto, A., Takeba, G., Shibata, D. Tanaka, K. (1990). Phytochrome-mediated activation of the gene for cytosolic glutamine synthetase (GSi) during inhibition of photosensitive lettuce seeds. Plant Molecular Biology 15, 317-23. 

Sengupta-Gopalan, C. Pitas, J.W. (1986). Expression of nodule-specific glutamine synthetase genes during nodule development in soybeans. Plant Molecular Biology 7, 189-99. 

Robertson, D. L., and Tartar, A. (2006). Evolution of glutamine synthetase in heterokonts evidence for endosymbiotic gene transfer and the early evolution of photosynthesis. Molecular Biology and Evolution. 23(5), 1048-1055 doi 10.1093/molbev/msjll0. 

EC nomenclature for enzymes A classification of ENZYMES according to the Enzyme Commission of the International Union of Biochemistry and Molecular Biology. Enzymes are allocated four numbers, the first of which defines the type of reaction catalyzed the next two define the substrates, and the fourth is a catalogue number. Categories of enzymes are EC 1, oxidoreduc-tases EC 2, transferases EC 3, hydrolases EC 4, lyases EC 5, isomerases EC 6, ligases (Synthetases). 

Fig. 6.11 Linker glycan for chondroitin sulfate synthesis. In the Golgi, the serine residue -OH group on a protein activates a specific synthetase in the Golgi membrane to transfer UDP-xylose. UDP is lost in making the attachment shown. UDP-activated galactose and glucuronate are then added by other synthetases before chondroitin sulfate synthetase is activated each donor loses its UDP unlike hyaluronan synthesis. Keratan sulfate is added different linker glycans (Adapted from Fig. 19-39 in The Molecular Biology of the Cell. B. Alberts et al., 4th Ed. 2002. Garland Science, Taylor Francis Group, New York)...

Recently, we established a GSH-knockdown rat model for the prediction of human hepatotoxicity (Akai et al. 2007). An adenovirus vector with short hairpin RNA against rat y-glutamylcysteine synthetase (GCS) heavy chain subunit was constructed and used to knockdown GSH synthesis. This rat model, with an 80% decreased hepatic GSH level, demonstrated a high sensitivity for acetaminophen-induced hepatotoxicity. With the advance of molecular biology, novel animal models will be established and applied to drug development in the near future. 

Kobayashi, K., Rosenbloom, C., Beaudet, A.L., O Brien, W.E., 1991. Additional mutations in argininosuccinate synthetase causing citrullinemia. Molecular Biology and Medicine 8, 95-100. 

RNA viruses (2) and the interaction of aminoacyl-tRNA synthetase with tRNA (4,5). Reference (6) is a review of the method as applied to biological structures. Before we describe a study in some detail, let us discuss the usefulness of this very low resolution structural information in understanding the molecular biology of the interaction. 

The reactions of the shikimate pathway pose a number of interesting questions of both a mechanistic and stereochemical nature. Detailed studies have been made of the DAHP synthetase, 3-dehydroquinate dehydratase, 5-enolpyruvylshikimate-3-phosphate synthetase and chorismate synthetase reactions which have added further important knowledge to this area of molecular biology. Whilst these investigations have done nothing to detract from the important dictum that cells obey the laws of chemistry , they have nevertheless revealed some of the distinctive facets of enzyme chemistry and have highlighted some of the important differences between enzyme and relat chemically catalysed reactions. 

S. J. Hughes, J. A. Tanner, A. D. Hindley, A. D. Miller and I. R. Gould, Functional asymmetry in the lysyl-tRNA synthetase explored by molecular dynamics, free energy calculations and experiment, BMC Structural Biology, 2003, 3, 5. 

Although a great deal is known about the chemical composition of the mitochondrial membrane and it is established that the membrane contains a number of catalytic proteins e.g., the ATPase synthetase system, an ion transport molecular machinery and electron transport chain), the topological distribution of these proteins in the membrane is not known. All topological models proposed are at present hypothetical [177]. However, it is accepted that the mitochondrial membrane, like most if not all biological membranes, is of the fluid mosaic model and is composed of a lipid bilayer traversed by proteins (see plasma membrane in Chapter 16). Electron microscopic studies of the freeze-edge fractured faces of the outer and the inner membrane [178] indicate that the proteins are asymmetrically distributed not only when the inner is compared to the outer membrane, but also when the inner and outer faces of each of the fractured membranes are compared (Table 1-3). 

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