Interaction of Mn2+ and MnATP2- with the allosteric sites of AMP nucleosidase.
Year: 1980
Type: article
Abstract: ~AMP nucleosidase is activated allosterically by MnATPZ-.Studies of the interaction of MnZ+ and MnATPZ-with the allosteric sites of the enzyme indicate that both the manganese ion and ATP interact with enzyme protein.Activation of AMP nucleosidase by MnATP2-is strongly cooperative, giving slopes of -3 in Hill plots and an So.s value of 8 PM.Free Mn2+ competes with the MnATP2-complex for the allosteric sites and gives inhibition curves with two distinct inhibition constants.Saturation of empty allosteric sites with Mn2+ (Ki = 25 PM) causes partial inhibition while displacement of MnATPZ-by Mn2+ (Ki = 1.5 mM) causes complete inhibition.Binding studies with MnATPZ-indicate six sites for MnATPZ-interaction.Three of these sites have an apparent dissociation constant of 6.5 PM, while the remaining three sites have an apparent dissociation constant of 500 PM.The first three sites appear to be the functional allosteric entities since full activation occurs before there is significant saturation of the remaining three MnATP2-sites.In the presence of formycin-5'-P04, a proposed transition state analog of the enzyme, the two classes of MnATP2-sites give apparent dissociation constants of approximately 1.7 p~ and
Source: Journal of Biological Chemistry
Authors: V.L. Schramm, G.H. Reed
Institutions: University of Pennsylvania, Temple University
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W3184626