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Agonist‐stimulated high‐affinity GTPase in Dictyostelium membranes
Author(s) -
Snaar-Jagalska B.Ewa,
Jakobs Karl H.,
Van Haastert Peter J.M.
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)80302-8
Subject(s) - gtpase , dictyostelium discoideum , gtp' , pertussis toxin , stimulation , g protein , biochemistry , biology , small gtpase , microbiology and biotechnology , forskolin , receptor , biophysics , enzyme , signal transduction , endocrinology , gene
GTP hydrolysis in Dictyostelium discoideum membranes is caused by a low ( K m > 1 mM) and a high affinity ( K m 6.5 μM) GTPase. cAMP enhances GTP hydrolysis apparently by increasing the affinity of the high affinity GTPase (stimulated K m 4.5 μM); the low affinity GTPase was not affected by cAMP. Stimulation of GTP hydrolysis by cAMP was maximal at early time points and declined thereafter. A half‐maximal stimulation of GTPase occurred at 3 μM cAMP and the specificity of cAMP derivatives for stimulation of GTPase activity showed a close correlation with the specificity for binding to the cell surface cAMP receptor. Treatment of D. discoideum cells with pertussis toxin decreased the cAMP‐induced stimulation of GTPase from 42 ± 6% in control cells to 17 ± 9% in pertussis toxin‐treated cells. These results suggest that the interaction of cAMP with its surface receptor leads to stimulation of high affinity GTPase in D. discoideum membranes. At least one of those enzymes may represent a guanine nucleotide‐binding protein sensitive to pertussis toxin.