skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Characteristics of intracellular Ca/sup 2 +/ release mediated by GTP

Abstract

GTP (but not non-hydrolysable analogs) promotes microsomal Ca/sup 2 +/ release from several tissues provided polyethylene glycol (PEG) is present in the incubation medium. GTP-mediated Ca/sup 2 +/ release from insulinoma or rat liver microsomes is slow and proceeds only after a lag. Rapid Ca/sup 2 +/ release promoted by inositol trisphosphate occurs in microsomes from insulinoma but not liver unless GTP is present. Further experiments indicate that the effects of GTP are dependent on the ionic strength of the incubation medium, the intravesicular Ca/sup 2 +/ load, and are retained upon salt-washing or further purification of the microsomes. GTP-mediated Ca/sup 2 +/ release is halted by an excess of GTP..gamma..S added during the lag or at any stage of Ca/sup 2 +/ release indicating the continued requirement for GTP to sustain release. However, analogs do not promote Ca/sup 2 +/ re-accumulation when added after the release is complete. The relative potency with which analogs inhibit GTP-mediated Ca/sup 2 +/ release was similar to their ability to displace bound ..cap alpha../sup 32/P-GTP. 7-Methyl GTP was found to be relatively ineffective at releasing Ca/sup 2 +/ or displacing ..cap alpha../sup 32/P-GTP. PEG stimulated the rate of ..cap alpha../sup 32/P-GTP binding withoutmore » affecting the equilibrium value. The lack of a similar effect on /sup 35/S-GTP-..gamma..S binding is consistent with previous studies suggesting that the step affected by PEG is GTP hydrolysis. Experiments on the purification of microsomal high affinity GTPase will be presented and the physiological relevance of this Ca/sup 2 +/ release mechanism will be assessed.« less

Authors:
; ;
Publication Date:
Research Org.:
Univ. of Pennsylvania, Philadelphia
OSTI Identifier:
6029559
Report Number(s):
CONF-870644-
Journal ID: CODEN: FEPRA; TRN: 87-037138
Resource Type:
Conference
Journal Name:
Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)
Additional Journal Information:
Journal Volume: 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; CALCIUM COMPOUNDS; SECRETION; GUANYLIC ACID; BIOCHEMICAL REACTION KINETICS; PHOSPHOHYDROLASES; FRACTIONATION; CATIONS; LIVER; MICROSOMES; PHOSPHORUS 32; POLYETHYLENE GLYCOLS; RATS; TRACER TECHNIQUES; ACID ANHYDRASES; ALCOHOLS; ALKALINE EARTH METAL COMPOUNDS; ANIMALS; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; BODY; CELL CONSTITUENTS; CHARGED PARTICLES; DAYS LIVING RADIOISOTOPES; DIGESTIVE SYSTEM; ENZYMES; GLANDS; GLYCOLS; HYDROLASES; HYDROXY COMPOUNDS; IONS; ISOTOPE APPLICATIONS; ISOTOPES; KINETICS; LIGHT NUCLEI; MAMMALS; NUCLEI; NUCLEOTIDES; ODD-ODD NUCLEI; ORGANIC COMPOUNDS; ORGANIC POLYMERS; ORGANOIDS; ORGANS; PHOSPHORUS ISOTOPES; POLYMERS; RADIOISOTOPES; REACTION KINETICS; RODENTS; SEPARATION PROCESSES; VERTEBRATES; 550201* - Biochemistry- Tracer Techniques

Citation Formats

Rice, H L, Williamson, J R, and Joseph, S K. Characteristics of intracellular Ca/sup 2 +/ release mediated by GTP. United States: N. p., 1987. Web.
Rice, H L, Williamson, J R, & Joseph, S K. Characteristics of intracellular Ca/sup 2 +/ release mediated by GTP. United States.
Rice, H L, Williamson, J R, and Joseph, S K. 1987. "Characteristics of intracellular Ca/sup 2 +/ release mediated by GTP". United States.
@article{osti_6029559,
title = {Characteristics of intracellular Ca/sup 2 +/ release mediated by GTP},
author = {Rice, H L and Williamson, J R and Joseph, S K},
abstractNote = {GTP (but not non-hydrolysable analogs) promotes microsomal Ca/sup 2 +/ release from several tissues provided polyethylene glycol (PEG) is present in the incubation medium. GTP-mediated Ca/sup 2 +/ release from insulinoma or rat liver microsomes is slow and proceeds only after a lag. Rapid Ca/sup 2 +/ release promoted by inositol trisphosphate occurs in microsomes from insulinoma but not liver unless GTP is present. Further experiments indicate that the effects of GTP are dependent on the ionic strength of the incubation medium, the intravesicular Ca/sup 2 +/ load, and are retained upon salt-washing or further purification of the microsomes. GTP-mediated Ca/sup 2 +/ release is halted by an excess of GTP..gamma..S added during the lag or at any stage of Ca/sup 2 +/ release indicating the continued requirement for GTP to sustain release. However, analogs do not promote Ca/sup 2 +/ re-accumulation when added after the release is complete. The relative potency with which analogs inhibit GTP-mediated Ca/sup 2 +/ release was similar to their ability to displace bound ..cap alpha../sup 32/P-GTP. 7-Methyl GTP was found to be relatively ineffective at releasing Ca/sup 2 +/ or displacing ..cap alpha../sup 32/P-GTP. PEG stimulated the rate of ..cap alpha../sup 32/P-GTP binding without affecting the equilibrium value. The lack of a similar effect on /sup 35/S-GTP-..gamma..S binding is consistent with previous studies suggesting that the step affected by PEG is GTP hydrolysis. Experiments on the purification of microsomal high affinity GTPase will be presented and the physiological relevance of this Ca/sup 2 +/ release mechanism will be assessed.},
doi = {},
url = {https://www.osti.gov/biblio/6029559}, journal = {Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)},
number = ,
volume = 46:6,
place = {United States},
year = {Fri May 01 00:00:00 EDT 1987},
month = {Fri May 01 00:00:00 EDT 1987}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share: