Vanadium (V) was rediscovered for biology as a “muscle inhibitor factor” when it was found in commercial ATP prepared from equine muscle almost thirty years ago. Since
then it has been used as a molecular probe of the mechanisms of several enzyme reactions involving hydrolysis of phosphate
ester bonds. Besides acting as a phosphate analogue, vanadate has also the potential to exhibit biological activities through oligomeric vanadate species. Among the vanadate oligomers, decavanadate is one of the most potent inhibitors and has revealed an excellent kinetic and spectroscopic
probe. This is particularly relevant for myosin, the major muscle ATPase which along with actin is able to convert the
chemical energy of ATP hydrolysis into mechanical work.
Apparently, vanadate is able to populate different conformational states of the myosin ATPase cycle depending
on its oligomerization state. While monomeric vanadate (VO4
3-) mimics the transition state for the g-phosphate hydrolysis blocking myosin in a pre-power stroke state, decameric vanadate (V10O28 6-) induces the formation of the
intermediate myosin·MgATP·V10 complex blocking the actomyosin cycle in a pre-hydrolysis state. These recent
findings, that are now reviewed, point out to the importance of taking into account vanadate species variety in studies
describing the interaction of vanadate with biological systems and incite the use of decavanadate as a biochemical tool to the elucidation of muscle contraction regulation
