Valyl tRNA synthetase

Hashimoto T (1998) Secondary absence of mitochondria in Giardia lamblia and Trichomonas vaginalis revealed by valyl-tRNA synthetase phylogeny. Proc Natl Acad Sci USA 95 6860-6865... 

Figure 6.4 Experimental curves for equilibrium gel filtration, (a) The 1-mL tuberculin syringe was incubated in 109-pAf[14C]valine (O) or 109-/zM[14C]valine and 4-mM ATP ( ). Then 100 fjL of a solution of 26-fiM valyl-tRNA synthetase was added to the same solution. Stoichiometries of 0.8 and 1.1, respectively, were found for the binding of the amino acid. Note the return to baseline between the peak and the trough— the mark of a good equilibrium gel filtration experiment, (b) An artifact-induced double peak obtained from the binding of [y-32P]ATP and valine to the enzyme. Some of the labeled ATP hydrolyzed to [32P]orthophosphate, which traveled down the column faster than the fy-32P]ATP did.

Fiqure 13.1 The binding cavity at the active site of the isoleucyl-tRNA synthetase must be able to bind valine as it binds the larger isoleucine. The active site of the valyl-tRNA synthetase cannot exclude threonine, because it is isosteric with valine. 

Fukai, S., Nureki, O., Sekine, S., Shimada, A., Tao,J., Vassylyev, D. G., and Yokoyama, S. (2000). Structural basis for double-sieve discrimination of L-valine from L-isoleucine and L-threonine by the complex of tRNA(Val) and valyl-tRNA synthetase. Cell 103, 793-803. 

Hashimoto T (1998) Secondary absence of mitochondria in Giardia lamblia and Trichomonas vaginalis revealed by valyl-tRNA synthetase phylogeny. Proc Natl Acad Sci USA 95 6860-6865 Hausmann A, Guilar Netz DJ, Balk J, Pierik AJ, Muhlenhoff U, Lill R (2005) The eukaryotic P loop NTPase Nbp35 an essential component of the cytosolic and nuclear iron-sulfur protein assembly machinery. Proc Natl Acad Sci USA 102 3266-3271 Horner DS, Foster PG, Embley TM (2000) Iron hydrogenases and the evolution of anaerobic eukaryotes. Mol Biol Evol 17 1695-1709... 

Table 1 Percentage inhibition of a range of spinach chloroplast aaTRS s by sulfamoyladenosines at lOpM (ND = Not Determined, LTRS = leucyl-tRNA synthetase, ITRS = isoleucyl-tRNA synthetase, VTRS = valyl-tRNA synthetase, ATRS = Alanyl-tRNA synthetase, GTRS = glycyl-tRNA synthetase)...

S. Fukai, O. Nureki, S. Sekine, A. Shimada, J. Tao, D.G. Vassylyev, and S. Yokoyama. 2000. Structural basis for doublesieve discrimination of 1-valine from 1-isoleucine and 1-threonine by the complex of tRNA(Val) and valyl-tRNA synthetase Cell 103 793-803. (PubMed)... 

Singer, P. A., Levinthal, M., Williams, L. S. (1984). Synthesis of the isoleucyl- and valyl-tRNA synthetases and the isoleucine-valine biosynthetic enzymes in a threonine deaminase regulatory mutant of Escherichia coli K-12. J. Mol. Biol. 175, 39-55. 

In other words, isoleucine and valine stabilize the enzyme in the immature form. Their further observation that the immature form of threonine deaminase has an affinity for leucyl tRNA but not for valyl or isoleucyl tRNA is certainly of interest with respect to the obvious correlation with multivalent repression that is possible [16]. Hatfield and Burns propose that the leucyl tRNA-immature tetramer complex might be the holorepressor of the ilv genes or perhaps at least of the ilv ADE operon. If either valine or isoleucine were limiting, maturation of the enzyme would occur without interference by either leucine or leucyl tRNA, thus leading to derepression. Derepression would also occur when isoleucine and valine were both in sufficient excess to block maturation provided leucine were limiting so that the leucyl tRNA-immature tetramer complex could not be formed. The significance of this model has yet to be assessed, but it is difficult at present to account for the supposed involvement of the isoleucyl and valyl tRNA synthetases in multivalent repression. Nevertheless, this interesting observation should be kept in mind as a possible mechanism that could account for part of the phenomenon of multivalent repression when additional information is acquired. 

For the isoleucine-valine system, there is evidence for the involvement of valyl-tRNA synthetase (Eidlic and Neidhardt [97]) and isoleucyl-tRNA synthetase (Blatt and Umbarger [98]) in repression. Likewise, leucyl-tRNA synthetase has been implicated in the regulation of the formation of the leucine biosynthetic enzymes (Calvo et al. [99]). In multivalent repression of the branched-chain amino acids [100], all three aminoacyl-tRNA synthetases appear to play a role. Leucyl-tRNA has been proposed as a regulatory element (Hatfield and Burns [101]). 

Pyrimidine thetase and valyl tRNA synthetase Ribonuclease dihydro U stem and loop, and other regions Photosensitized inter- 143... 

J-Valerolactam, 218 L-Valine tRNA ligase, 152 Valyl-tRNA, 624 Valyl-tRNA synthetase, 90 Vinyl chlorides as inhibitors, 37, 38 Vinyl glycine, 33 synthesis of, 39, 40... 

Fig. 1 - Values of I(0)/C (C is the concentration in mg/ml) normalised to 1.00 for free valyl-tRNA synthetase at each [ D2O ] [ H2Oj ratio, and Rq plotted as functions of the molar ratio of tRNA to enzyme. Concentrations of protein were maintained constant at 7 mg/ml. The curves were calculated from an equilibrium model given in the text.

Figure 1 shows part of the data obtained in a study of the interaction of yeast valyl-tRNA synthetase with different RNA s (5). It is important to bear in mind that the curves in the H2O frames and in the 77% D2O frames are different views of the same reaction. 

Giege, Valyl-tRNA synthetase-tRNA interactions, J. Mol. Biol., 129 483 (1979). 

Still another set of T4-induced changes in the translation machinery awaits correlation with the in vivo regulation The pattern of transfer RNA and the properties of valyl tRNA synthetase change after T4 infection (Sueoka and Kano-Sueoka, 1964 Waters and Novelli, 1967 Kano-Sueoka, 1969 Weiss et al., 1968 McClain, 197O Chrispeels et al., 1968 Wilson, 1973). It is possible that these new tRNAs serve to increase the efficiency of translation of certain T4 genes containing codons which are only recognized by minor species of E, coli tRNA. 

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