Self-assembly on target membranes is one of the important properties of all dynamin family proteins. Drp6, a dynaminrelatedprotein in Tetrahymena, controls nuclear remodelling and undergoes cycles of assembly/disassembly on the nuclearenvelope. To elucidate the mechanism of Drp6 function, we have characterized its biochemical and biophysical propertiesusing size exclusion chromatography, chemical cross-linking and electron microscopy. The results demonstrate that Drp6readily forms high-molecular-weight self-assembled structures as determined by size exclusion chromatography andchemical cross-linking. Negative stain electron microscopy revealed that Drp6 assembles into rings and spirals at physiologicalionic strength. We have also shown that the recombinant Drp6 expressed in bacteria is catalytically active and itsGTPase activity is not enhanced by low salt. These results suggest that, in contrast to dynamins but similar to MxA, Drp6self-assembles in the absence of membrane templates, and its GTPase activity is not affected by ionic strength of the buffer.We discuss the self-assembly structure of Drp6 and explain the basis for lack of membrane-stimulated GTPase activity.