Comparison of the conformation and stability of the native dimeric, monomelic, tetrameric and the desensitized forms of the nucleotide pyrophosphatase from mung bean (Phaseolus aureus) seedlings.
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Date
1980-09
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Abstract
A homogenous and crystalline form of nucleotide pyrophosphatase (EC 3.6.1.9)
from Phaseolus aureus (mung bean) seedlings was used for the study of the regulation of enzyme
activity by adenine nucleotides. The native dimeric form of the enzyme had a helical content of
about 65% which was reduced to almost zero values by the addition of AMP. In addition to this
change in the helical content, AMP converted the native dimer to a tetramer. Desensitization of
AMP regulation, without an alteration of the molecular weight, was achieved either by reversible
denaturation with 6 Μ urea or by passage through a column of Blue Sepharose but additionof phydroxymercuribenzoate
desensitized the enzyme by dissociating the native dimer to a monomer.
The changes in the quaternary structure and conformation of the enzyme consequent to AMP
interaction or desensitization were monitored by measuring the helical content, EDTA inactivation
and Zn2+ reactivation, stability towards heat denaturation, profiles of urea denaturation and
susceptibility towards proteolytic digestion. Based on these results and our earlier work on this
enzyme, we propose a model for the regulation of the mung bean nucleotide pyrophosphatase
by association-dissociation and conformational changes. The model emphasizes that multiple
mechanisms are operative in the desensitization of regulatory proteins.
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Keywords
Phaseolus aureus, nucleotide pyrophosphatase, regulation, desensitization, conformational changes, circular dichroism, optical rotatory dispersion
Citation
Reddy A R Venugopala, Balakrishnan C V, Sobhanaditya J, Ravindranath S D, Ananthanarayanan V S. Comparison of the conformation and stability of the native dimeric, monomelic, tetrameric and the desensitized forms of the nucleotide pyrophosphatase from mung bean (Phaseolus aureus) seedlings. Journal of Biosciences. 1980 Sept; 2(3): 211-225.