  We develop a general theory of microtubule (MT) deformations by molecular
motors generating internal force doublets within the MT lattice. We describe
two basic internal excitations, the S and V shape, and compare them with
experimental observations from literature. We explain the special role of
tubulin vacancies and the dramatic deformation amplifying effect observed for
katanin acting at positions of defects. Experimentally observed shapes are used
to determine the ratio of MT shear and stretch moduli ($\approx
6\times10^{-5}$) and to estimate the forces induced in the MT lattice by
katanin (10's of pN). For many motors acting on a single MT we derive
expressions for the end-to-end distance reduction and provide criteria for
dominance of this new effect over thermal fluctuations. We conclude that
molecular motors if acting cooperatively can ''animate'' MTs from within the
lattice and induce slack even without cross-bridging to other structures, a
scenario very much reminiscent of the motor driven axoneme.
