Tektins are cytoskeletal proteins. They have been demonstrated in such cellular sites as centrioles, basal bodies, and along ciliary and flagellar doublet microtubules. Tektins form unique protofilaments, organized as longitudinal polymers of tektin heterodimers with axial periodicity matching tubulin. Tektin polypeptides consist of several alpha-helical regions that are predicted to form coiled coils. Indeed, tektins share considerable structural similarities with intermediate filament proteins. Possible functional roles for tektins are: stabilisation of tubulin protofilaments; attachment of A and B-tubules in ciliary/flagellar microtubule doublets and C-tubules in centrioles; binding of axonemal components.