The identification of a conserved domain in both spartin and spastin, mutated in hereditary spastic paraplegia

Multiple sequence alignment has revealed the presence of a sequence domain of ∼80 amino acids in two molecules, spartin and spastin, mutated in hereditary spastic paraplegia. The domain, which corresponds to a slightly extended version of the recently described ESP domain of unknown function, was also identified in VPS4, SKD1, RPK118, and SNX15, all of which have a well established and consistent role in endosomal trafficking. Recent functional information indicates that spastin is likely to be involved in microtubule interaction. With this new information relating to its likely function, we propose the more descriptive name ‘MIT’ (contained within m icrotubule- i nteracting and t rafficking molecules) for the domain and predict endosomal trafficking as the principal functionality of all molecules in which it is present.