The intrinsically disordered protein (IDP) stathmin plays an important 
regulatory role in cytoskeletal maintenance through its helical binding to 
tubulin and microtubules. However, it lacks a stable fold in the absence of its 
binding partner. Although stathmin has been a focus of research over the past 
two decades, the solution-phase conformational dynamics of this IDP are poorly 
understood. It has been reported that stathmin is purely monomeric in solution 
and that it bears a short helical region of persistent foldedness, which may act 
to nucleate helical folding in the C-terminal direction. Here we report a 
comprehensive study of the structural equilibria local to this region in 
stathmin that contradicts these two claims. Using the technique of electron 
paramagnetic resonance (EPR) spectroscopy on spin-labeled stathmin mutants in 
the solution-phase and when immobilized on Sepharose solid support, we show that 
all sites in the helical nucleation region of stathmin exhibit multiple spectral 
components that correspond to dynamic states of differing mobilities and 
stabilities. Importantly, a state with relatively low mobility dominates each 
spectrum with an average population greater than 50%, which we suggest 
corresponds to an oligomerized state of the protein. This is in contrast to a 
less populated, more mobile state, which likely represents a helically folded 
monomeric state of stathmin, and a highly mobile state, which we propose is the 
random coil conformer of the protein. Our interpretation of the EPR data is 
confirmed by further characterization of the protein using the techniques of 
native and SDS PAGE, gel filtration chromatography, and multiangle and dynamic 
light scattering, all of which show the presence of oligomeric stathmin in 
solution. Collectively, these data suggest that stathmin exists in a diverse 
equilibrium of states throughout the purported helical nucleation region and 
that this IDP exhibits a propensity toward oligomerization.