COUPLING BETWEEN CATALYSIS AND OLIGOMERIC STRUCTURE IN NUCLEOSIDE DIPHOSPHATE KINASE

A dimeric Dictyostelium nucleoside diphosphate kinase has been stabili zed by the double mutation P100S-N150stop which targets residues invol ved in the trimer interface (Karlsson, A, Mesnildrey S., Xu, Y., Morer a, S., Janin, J., and Vernon, M. (1996) J, Biol. Chem. 271, 19928-1993 4), The reassociation of this dimeric form into a hexamer similar to t he wild-type enzyme is induced by the presence of a nucleotide substra te, Equilibrium sedimentation and gel filtration experiments, as well as enzymatic activity measurements, show that reactivation of the enzy me closely parallels its reassociation, A phosphorylatable intermediat e with low activity participates ist the association pathway while the dimeric form is shown totally devoid of enzymatic activity, Our resul ts support the hypothesis that different oligomeric species of nucleos ide diphosphate kinase are involved in different cellular processes wh ere the enzymatic activity is not required.