Hydrogen bonding tyrosyl tRNA synthetase

Figure 4.18 Side chains of the tyrosyl-tRNA synthetase that form hydrogen bonds to tyrosyl adenylate. Green residues are from p strand 2 and the following loop regions, yellow residues are from the loop after P strand S, and brown residues are from the a helix before P strand S. (Adapted from T. Wells and A. Fersht, Nature 316 656-657, 1985.)...

Chemical reactivity and hydrogen bonding 320 Proton-transfer behaviour 321 Intramolecular hydrogen-bond catalysis 344 Enzyme catalysis and hydrogen bonding 354 Chymotrypsin 354 Thermolysin 355 Carboxypeptidase 355 Tyrosyl tRNA synthetase 356 Summary 366 Acknowledgements 367 References 367... 

Table 17 Effects of hydrogen bonds on free energy differences as measured by AG.pp in tyrosyl activation catalysed by mutations of tyrosyl tRNA synthetase (44).

Figure 15.1 Residues of the tyrosyl-tRNA synthetase that form hydrogen bonds with tyrosyl adenylate.

Energy of individual hydrogen bonds in a protein tyrosyl-tRNA synthetase as a test case. When an enzyme interacts with its substrate, the bound water molecules... 

Fig. 19.20. Schematic drawing of hydrogen-bonding interactions between the enzyme tyrosyl-tRNA synthetase and the substrate analog tyrosyl adenylate. The enzyme groups interacting with tyrosyl adenylate are boxed, MC indicates main-chain C=0 or N-H groups [647]...

In general, the data obtained from point mutations of tyrosyl-tRNA synthetase demonstrate that hydrogen bonding contributes significantly to the specificity of... 

Fersht et al., in a very well-known study of the binding of tyrosyl-tRNA synthetase to its substrate [39], found that deletion of a strong hydrogen bond donor or acceptor from the enzyme reduced the free energy of binding by only 2.1-6.3 kJ mol , whereas removal of the partner of a very strong donor or acceptor weakened binding by an additional 12 kJ mol . Data on mutants of ribonuclease Tl by Shirley et al. 

Figure 3-3. Hydrogen bonds between the tyrosyl-tRNA synthetase and tyrosyl adenylate.

Hydrogen-bonding interactions between the substrate and enzyme have been explored in depth in the catalytic mechanism of tyrosyl-tRNA synthetase (tyro-sine-tRNA ligase). The enzyme-catalyzed reaction occurs in two steps ... 

FtG. 12. Interactions between the transition state for the formation of Tyr-AMP and hydrogen-bonding (or charged) side chains that were deduced from site-directed mutagenesis of tyrosyl-tRNA synthetase. The overall site may be classified in terms of subsites as indicated and described in the text. [Reprinted with permission from Ref. (157).]... 

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