We consider an open Heisenberg quantum spin chain, coupled at the ends to boundary
reservoirs polarized in different directions, which sets up a twisting gradient across the chain.
We demonstrate that the exact nonequilibrium steady state of the chain driven by boundary Lindblad operators can be constructed explicitly with a matrix product ansatz where the matrices satisfy the quantum algebra Uq[SU(2)]. Using this matrix product ansatz in the isotropic case, we calculate explicitly the magnetization profiles and magnetization currents.