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


  • eng

Conference Location

  • England