Tryptophanyl-tRNA synthetase

The 37-kDa 334-residue subunits of the dimeric type I tryptophanyl-tRNA synthetase238 are the smallest known the largest bacterial synthetase is an alanine-specific type II tetramer with 95-kDa 875-residue subunits.239 Gene deletions show that a much smaller core, comparable in size to that of the tryptophanyl-tRNA synthetase, is needed for amino acid activation. The synthetases share little sequence homology except for a short 11-residue part of the adenylate binding site near the N terminus.240 241 Some of the synthetases contain bound zinc ions.225,242... 

An example of this approach is illustrated in Fig. 3.4. The graph in the center is a two-dimensional slice of a four-dimensional surface over which [protein], ([protein] X [precipitant]), pH, and temperature were varied, in attempts to find optimal crystallization conditions for the enzyme tryptophanyl-tRNA synthetase. Note that this surface samples the rectangular region [protein] versus ([protein] X [precipitant]), mentioned earlier. The height of the surface is the score for the crystallization. Surrounding the graph are photos of typical crystals obtained in multiple trials of each set of conditions. None of the trial conditions were near the peak of the surface. The... 

Figure 3.4 Optimization of conditions for crystallization of tryptophanyl-tRNA synthetase. Photo insets show crystals obtained from various conditions represented by points on the surface. Coordinates of the surface are protein concentration (PROTEIN), product of protein concentration and precipitant concentration (PRO-PPNT), and the shape of the crystal as reflected by the ratio of its two smallest dimensions, width and length (WL RATIO). From C. W. Carter, in Methods in Enzymology 276, C. W. Carter and R. M. Sweet, eds., Academic Press, New York, 1997, p. 75. Reprinted with permission.

Pitram, S.M., Druzina, Z., Fokin, V.V., Schimmel, P, Sharpless, K.B. Inhibitors of tryptophanyl-tRNA synthetase from Plasmodium falciparum via in situ click chemistry. Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, 10-14 September 2006. 

Therefore, that tryptophanyl-tRNA synthetase production in the apicoplast is upregulated (in the chloroquine-induced microarray data) may suggest that this efflux process was made possible (caused) by the apicoplast, the mini bacterium living inside the malaria parasite. Ralph et al. (45) state that it is not yet clear what the key function of the apicoplast is but the organelle is clearly indispensable. Curiously though, parasites cured of their apico-plasts do not die immediately. Rather, they fail to invade new host cells successfully. This suggests that apicoplasts provide some component essential to invasion and or [sic] establishment of the para-sitophorous vacuole in the host cell (46, 47). 

The indole derivative 12, a synthetic analogue of the antimicrobial natural product chuangxinmycin, is an inhibitor of bacterial tryptophanyl tRNA synthetase and displays antibacterial activity <2002BML3171>. 

Kise Y, Lee SW, Park SG, Fukai S, Sengoku T, Ishii R, Yokoyama S, Kim S, Nureki O. A short peptide insertion crucial for an-giostatic activity of human tryptophanyl-tRNA synthetase. Nat. Struct. Mol. Biol. 2004 11 149-156. 

Lee, C. C., Craigen, W. J., Munzy, D. M., Harlow, E., Caskey, C. T. (1990). Cloning and expression of a mammalian peptide chain release factor with sequence similarity to tryptophanyl-tRNA synthetase. Proc. Natl. Acad. Sci. USA 87, 3508-3512. 

Rubin et al.346 reported the cloning and characterization of a cDNA, representing a gene where expression is upregulated in INF-treated cells. This gene encodes a protein that has sequence homology with and the biological activity of a tryptophanyl-tRNA synthetase. 

Rubin, B. Y., Anderson, S. L., Xing, L., Powell, R. J., and Tate, W. P., Interferon induces tryptophanyl-tRNA synthetase expression in human fibroblasts, ]. Biol. Chem., 266, 24245, 1991. 

Several other purine nucleotide derivatives with alkyl halide substituents have appeared in the literature, including adenosine S -chloromethane phosphonate, adenosine 5 -chloromethylpyrophosphate, and adenosine 5 -()8-bromoethane phosphonate) (287-291). These compounds have been evaluated as affinity labels of such nucleotide-binding enzymes as leucyl- and tryptophanyl-tRNA synthetases (leucine- and tryptophan-tRNA ligases), phosphorylase b, and cAMP-... 

Recently, scientists at the Scripps Research Institute in the USA have discovered that human tyrosyl-tRNA synthetase does two jobs. In addition to its regular job in protein synthesis, i.e. charging tRNA with tyrosine, it can also stimulate the growth of blood vessels. Also, another aminoacyl-tRNA synthetase, tryptophanyl-tRNA synthetase, not only charges tRNA with tryptophan, but it also inhibits the formation of new blood vessels. This research work has clinical potential. Tyrosyl-tRNA synthetase is pro-angiogenic and could be used to promote the growth of new blood vessels in some types of cardiovascular disease. On the other hand, tryptophanyl-tRNA synthetase is anti-angiogenic and could be used to reduce blood vessel invasion in cancer. 

Fluorescence based structural analysis of tryptophan analogue— AMP formation in single tryptophan mutants of Bacillus stearothermophUus tryptophanyl-tRNA synthetase. Biochemistry 42 (2003) 14994-15002. 

There have not been any reports of strains resistant to tryptophan analogs as a result of mutant tryptophanyl-tRNA synthetase. However, three laboratories have independently isolated strains of E. coli with partial tryptophan auxotrophies (bradytrophs) as a result of mutations in what appears to be the structural gene, trpS, for tryptophanyl-tRNA synthetase [187,188,214,215]. The partial auxotrophy was overcome by either tryptophan or indole supplementation but not by anthranilate. 

All three laboratories [187,188,215] reported evidence that the trpS mutant strains were defective in tryptophanyl-tRNA synthetase activity by in vitro tests. Doolittle and Yanofsky [187] found little or no enzyme activity in extracts of various mutant strains, and some displayed distinct temperature sensitivities. Substrate protected some of the defective enzymes from inactivation. Two of the mutant enzyme extracts were examined for K , values which were found to be ten times as high as that of wild type [187]. Ito et al. [188] studied one trpS mutant in detail and determined that the tryptophanyl-tRNA synthetase was very unstable but could be stabilized by tryptophan in the presence of ATP. 

In E. coli, tryptophanyl-tRNA synthetase mutants are known (Hiraga et al. [92] Kano et al. [93] Ito et al. [94, 95]), in which tryptophan biosynthetic enzymes are neither completely repressible nor normally derepressible. A role of the synthetase in repression by tryptophan is thus indicated. Evidence against a function of tiypt-ophanyl-tRNA as corepressor has been furnished by Mosteller and Yanofsky [96], who showed that the charging of tRNA does not correlate with repression by tryptophan. Nevertheless, certain possibilities of an involvement of tryptophanyl-tRNA in the repressive process exist for example, a very low concentration of charged tRNA (undetectable by the method used) may be sufficient for repression [96]. 

Tryptophanyl-tRNA synthetase l-Tryptophan tRNA ligase (AMP-forming) 6.1.1.2 237... 

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