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Histone II-A activates the glucose-6-phosphatase system without microsomal membrane permeabilization
B A Pederson1, J D Foster, R C Nordlie
1Department of Biochemistry and Molecular Biology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202, USA.
Archives of Biochemistry and Biophysics
|August 29, 1998
Summary
Histone II-A activates the glucose-6-phosphatase (Glc-6-Pase) system without permeabilizing microsomal membranes, unlike alamethicin. This study clarifies the distinct mechanisms by which these agents modulate Glc-6-Pase activity.
Area of Science:
- Biochemistry
- Enzymology
- Membrane Biology
Background:
- The glucose-6-phosphatase (Glc-6-Pase) system's latent activity is modulated by various agents.
- Detergents and alamethicin activate Glc-6-Pase by disrupting microsomal membranes.
- Histone II-A also activates Glc-6-Pase, but its mechanism of action is debated.
Purpose of the Study:
- To investigate whether histone II-A activates the Glc-6-Pase system through microsomal membrane permeabilization.
- To compare the mechanisms of activation by histone II-A, alamethicin, and Triton X-100.
Main Methods:
- Treatment of rat liver microsomes with Triton X-100, alamethicin, or histone II-A.
- Assessment of Glc-6-Pase system activation.
- Evaluation of the effects of alamethicin and histone II-A on inhibition by thiol-directed reagents (N-bromoacetylethanolamine phosphate and 3-mercaptopicolinate).
Main Results:
- Triton X-100, alamethicin, and histone II-A equally activated the Glc-6-Pase system.
- Alamethicin abolished the inhibitory effects of thiol-directed reagents, indicating membrane permeabilization.
- Histone II-A did not abolish the inhibitory effects of thiol-directed reagents, suggesting activation without membrane permeabilization.
Conclusions:
- Histone II-A activates the Glc-6-Pase system without altering microsomal membrane integrity.
- Alamethicin activates Glc-6-Pase by permeabilizing microsomal membranes, consistent with previous findings.
- The study elucidates distinct mechanisms for Glc-6-Pase activation by different agents.