May 25, 1976

Studies on tyrosine residues in porcine muscle adenylate kinase. Circular dichroism spectra and chemical modification with tetranitromethane

The Journal of Biological Chemistry
M Yazawa, L H Noda

Abstract

Substrate-induced conformational change of porcine muscle adenylate kinase (EC 2.7.4.3) is evidenced by a change in circular dichroism spectra in the near ultraviolet. In the absence of tryptophan in porcine muscle adenylate kinase, the spectral change may be assigned to a perturbation of tyrosine chromophore(s). The spectral change was specific for adenine nucleotide binding and was greater with ATP than with AMP. In the x-ray model, Tyr153 and Tyr154 are located at a hinge region of two domains which form a deep active site cleft and are therefore susceptible to conformational change on substrate binding. Adenylate kinase was treated with equimolar tetranitromethane. The yellow-colored product, separated from unmodified enzyme by substrate gradient elution on a phosphocellulose column, had about 1 mol of nitrotyrosine per mol of the enzyme by amino acid analysis and showed a slightly higher Km value than native enzyme for ADP (Km = 0.50 mM compared with 0.25 mM for native adenylate kinase). Spectrophotometric titration of nitroadenylate kinase gave pKa 8.4 for the dissociation constant of the nitrotyrosyl hydroxyl group. On binding ATP the pKa value increased to 9.0 while AMP binding caused very little change. By peptide mapp...Continue Reading

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Mentioned in this Paper

Tryptophan
Peptide Mapping
Plain X-ray
Macromolecular Alteration
AMP Binding
Plasma Protein Binding Capacity
Adenylate KINASE
Protein Conformation
Muscle
Radiographic Imaging Procedure

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