Polyethylene glycol‐stimulated microsomal GTP hydrolysis

FEBS Letters

Joseph, Suresh K.¹  Nicchitta, Christopher V.¹  Williamson, John R.¹ 

[1] The Department of Biochemistry & Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6089, USA

关键词: GTP hydrolysis;    Ca2+ release;    Polyethylene glycol;    Microsome;    PEG;    polyethylene glycol;    InsP3;    inositol 1;    4;    5-trisphosphate;    GMPPNP;    guanosine 5'-[β;    γimido] triphosphate;    GTPγS;    guanosine 5' -O-(3-thiotriphosphate);    AppNHp;    adenyl imidodiphosphate;    PVP;    polyvinylpyrrolidone;   

DOI  :  10.1016/0014-5793(86)81120-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 (K _m = 0.9 μM) GTPase. The effects of PEG reflect an increase in the V _max of this activity; no effects on K _m 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 GTPγS (K _i = 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.

【 授权许可】

Unknown