Polyethylene glycol-stimulated microsomal GTP hydrolysis. Relationship to GTP-mediated Ca2+ release.
Journal Article (Journal Article)
It has recently been observed that GTP mediates Ca2+ release from internal Ca2+ stores. In contrast to effects on permeabilized cells, GTP-dependent Ca2+ release in isolated microsomes requires the presence of polyethylene glycol (PEG). We have investigated the effects of PEG on microsomal GTPase activity and report that PEG stimulates a high-affinity (Km = 0.9 microM) GTPase. The effects of PEG reflect an increase in the Vmax of this activity; no effects on Km were observed. The concentration dependence for PEG-dependent stimulation of the high-affinity GTPase exactly mimicked that for GTP-dependent Ca2+ release. The stimulation of GTP hydrolysis by PEG was specific for the microsome fraction; only small effects were obtained with plasma membrane or cytosol fractions. As observed for GTP-dependent Ca2+ release, the microsomal PEG-stimulated GTPase was competitively inhibited by the GTP analog GTP gamma S (Ki = 60 nM). It is proposed that the PEG-stimulated GTPase may represent an intrinsic activity of the guanine nucleotide binding protein involved in the regulation of reticular Ca2+ fluxes.
Full Text
Duke Authors
Cited Authors
- Nicchitta, CV; Joseph, SK; Williamson, JR
Published Date
- December 15, 1986
Published In
Volume / Issue
- 209 / 2
Start / End Page
- 243 - 248
PubMed ID
- 3025017
International Standard Serial Number (ISSN)
- 0014-5793
Digital Object Identifier (DOI)
- 10.1016/0014-5793(86)81120-6
Language
- eng
Conference Location
- England