A soluble factor and GTP gamma S are required for Dictyostelium discoideum guanylate cyclase activity.
Amoeba of Dictyostelium discoideum show a rapid, transient cGMP synthesis in response to chemotactic stimulation. Using Mg(2+)-GTP as a substrate, guanylate cyclase (E.C. 4.6.1.2.) activity is found exclusively in the particulate fraction of Dictyostelium cells. Here we show that the activity is dependent on the presence of the non-hydrolysable GTP-analogue GTP gamma S, which itself is only a poor substrate for the enzyme under the prevailing conditions. Evidence is presented that a transient exposure of the enzyme to GTP gamma S is sufficient to constitutively activate the enzyme. GTP gamma S-dependent activity is found to require a factor that can be separated from the enzyme by washing the particulate fraction with low salt buffer. Addition of the soluble cell fraction to these washed membranes restores enzyme activity.
Schulkes
C C
CC
E.C. Slater Institute for Biochemical Research, University of Amsterdam, Netherlands.
Schoen
C D
CD
Arents
J C
JC
Van Driel
R
R
D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism; D003600:Cytosol / Q000502:physiology; D004023:Dictyostelium / Q000201:enzymology*; D004789:Enzyme Activation; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology*; D006162:Guanylate Cyclase / Q000302:isolation & purification / Q000378:metabolism*; D015398:Signal Transduction
D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006162:Guanylate Cyclase; D006152:Cyclic GMP