Tyrosine hydroxyl group

Smyth, D.G. (1967) Acetylation of amino and tyrosine hydroxyl groups./. Biol. Chem. 242, 1592-1598. Smyth, D.G., Blumenfeld, O.O., and Konigsberg, W. (1964) Reaction of N-ethylmaleimide with peptides and amino acids. Biochem. J. 91, 589. 

Imidazole, lysine amino groups, and tyrosine hydroxyl groups react with diethylpyrocarbonate... 

The binding of a hormone or growth factor (a ligand) to a dimeric receptor activates the protein kinase domain of the receptor which phosphorylates a number of tyrosine hydroxyl groups of the receptor itself. This autophosphorylation is followed by a variety of events, which include phosphorylation of tyrosine side chains of various other proteins.426 An-... 

A new motif for OP binding to tyrosine has been identified. Almost all proteins appear to be capable of binding OP covalently on tyrosine. Whether or not OP will bind to tyrosine in vivo will depend on the concentration of the protein, the concentration of the OP, and the ionization status of the tyrosine hydroxyl group. The latter factor appears to be dependent on the presence of nearby positively charged residues. 

In studies of the recombination of heme with globin Jope,. lope and O Brien (1949) have used the concept of bound tyrosine hydroxyl groups as a criterion of native character in globin, based on the spectropho-tometric study of the alkaline ionization process. They were able to show that globin preparations which were native according to this criterion could be classified as denatured on the basis of the position of their tryptophan fine-structure bands when recombined with heme. These results led them to suggest that the process of denaturation could be separated into several stages, even by spectroscopic techniques alone (see also Jope, 1949). 

The effects of alkali up to 0.1 N on the absorption spectrum of lysozyme are fully reversible, according to Fromageot and Schnek (1950) it is of interest to note that this enzyme is a protein which is remarkably resistant to denaturation (Fraenkel-Conrat, 1950). Insulin behaves similarly, and it may be surmised that in both these proteins the tyrosine hydroxyl groups are not bound. The pK value of 10.8 found by Fromageot and Schnek (1950) for lysozyme supports this view. The pK data for insulin are more complicated and have been discussed at length by Crammer and Neuberger (1943). 

For human serum albumin Tanford (1950) found by spectrophotometry that the ionization of the tyrosine hydroxyl groups was completely reversible up to pH 12. Measurements at the wavelength of the tyrosine anion maximum (2930 A.), uncorrected for the small tryptophan contribution, gave a pK of 11.7 for this process. Both the ultraviolet absorption and titration data for this protein could be quantitatively interpreted on the basis of complete freedom of all the 18 tyrosine hydroxyl groups in the molecule to ionize. In this respect human serum albumin thus resembles insulin and not ovalbumin. 

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